編輯:關於Android編程
本文實例講述了Android操作SQLite數據庫(增、刪、改、查、分頁等)及ListView顯示數據的方法。分享給大家供大家參考,具體如下:
由於剛接觸android開發,故此想把學到的基礎知識記錄一下,以備查詢,故此寫的比較啰嗦:
步驟如下:
一、介紹:
此文主要是介紹怎麼使用android自帶的數據庫SQLite,以及把後台的數據用ListView控件顯示
二、新建一個android工程——DBSQLiteOperate
工程目錄:
三、清單列表AndroidManifest.xml的配置為:
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.dboperate" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="8" /> <application android:icon="@drawable/ic_launcher" android:label="@string/app_name" > <!--單元測試 加這句--> <uses-library android:name="android.test.runner" /> <activity android:name=".DBSQLiteOperateActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> <instrumentation android:name="android.test.InstrumentationTestRunner" android:targetPackage="com.example.dboperate" android:label="Test for my app"/> </manifest>
四、main.xml配置清單:
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="horizontal" > <TextView android:id="@+id/name" android:layout_width="100dip" android:layout_height="wrap_content" android:text="@string/name" android:gravity="center"/> <TextView android:id="@+id/phone" android:layout_width="100dip" android:layout_height="wrap_content" android:text="@string/phone" android:gravity="center"/> <TextView android:id="@+id/amount" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/amount" android:gravity="center"/> </LinearLayout> <ListView android:id="@+id/listView" android:layout_width="fill_parent" android:layout_height="fill_parent" > </ListView> </LinearLayout>
五、item.xml配置清單:
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="horizontal" > <TextView android:id="@+id/name" android:layout_width="100dip" android:layout_height="wrap_content" android:text="@string/name" android:gravity="center"/> <TextView android:id="@+id/phone" android:layout_width="100dip" android:layout_height="wrap_content" android:text="@string/phone" android:gravity="center"/> <TextView android:id="@+id/amount" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/amount" android:gravity="center"/> </LinearLayout>
六、string.xml配置清單:
<?xml version="1.0" encoding="utf-8"?> <resources> <string name="hello">Hello World, DBSQLiteOperateActivity!</string> <string name="app_name">ExampleDBSQLiteOperate8</string> <string name="name">姓名</string> <string name="phone">電話</string> <string name="amount">存款</string> </resources>
七、DBSQLiteOperateActivity.java Activity類的源碼:
package com.example.dboperate; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import com.example.adapter.PersonAdapter; import com.example.domain.Person; import com.example.service.PersonService; import android.app.Activity; import android.database.Cursor; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.AdapterView; import android.widget.AdapterView.OnItemClickListener; import android.widget.ListView; import android.widget.SimpleAdapter; import android.widget.SimpleCursorAdapter; import android.widget.Toast; public class DBSQLiteOperateActivity extends Activity { ListView listView; PersonService personService; OnItemClickListener listViewListener; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); listViewListener = new OnItemClickListener(){ @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { //得到listView控件 ListView listView = (ListView)parent; //1、如果使用自定義適配器,返回的是Person對象 //得到該條目數據 // Person person = (Person)listView.getItemAtPosition(position); // //廣播出去 // Toast.makeText(getApplicationContext(), person.toString(), Toast.LENGTH_LONG).show(); //2、如果使用showList2()方法中的適配器時,則取得的值是不一樣的,返回的是cursor // Cursor cursor = (Cursor)listView.getItemAtPosition(position); // int personid = cursor.getInt(cursor.getColumnIndex("_id")); // Toast.makeText(getApplicationContext(), personid+"", Toast.LENGTH_LONG).show(); //3、如果使用showList()方法中的適配器時,則取得的值是不一樣的,返回的是map @SuppressWarnings("unchecked") Map<String,Object> map = (Map)listView.getItemAtPosition(position); String name = map.get("name").toString(); String personid = map.get("personid").toString(); Toast.makeText(getApplicationContext(), personid +"-"+ name, Toast.LENGTH_LONG).show(); } }; listView = (ListView) this.findViewById(R.id.listView); listView.setOnItemClickListener(listViewListener); personService = new PersonService(this); showList(); } private void showList() { List<Person> persons = personService.getScrollData(0, 50); List<HashMap<String,Object>> data = new ArrayList<HashMap<String,Object>>(); for(Person person : persons){ HashMap<String,Object> item = new HashMap<String,Object>(); item.put("name", person.getName()); item.put("phone", person.getPhone()); item.put("amount", person.getAmount()); item.put("personid", person.getId()); data.add(item); } SimpleAdapter adapter = new SimpleAdapter(this,data,R.layout.item, new String[]{"name","phone","amount"}, new int[]{R.id.name,R.id.phone,R.id.amount}); listView.setAdapter(adapter); } public void showList2(){ Cursor cursor = personService.getCursorScrollData(0, 50); //該適配器要求返回的結果集cursor必須包含_id字段,所以需要對取得結果集進行處理 SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,R.layout.item,cursor,new String[]{"name","phone","amount"}, new int[]{R.id.name,R.id.phone,R.id.amount} ); listView.setAdapter(adapter); } /** * 自定義適配器 */ public void showList3(){ List<Person> persons = personService.getScrollData(0, 50); /** * 第一個參數:上下文context,第二個參數:要顯示的數據,第三個參數:綁定的條目界面 */ PersonAdapter adapter = new PersonAdapter(this, persons, R.layout.item); listView.setAdapter(adapter); } }
八、person.java 實體類 源碼:
package com.example.domain; public class Person { private Integer id; private String name; private String phone; private Integer amount; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPhone() { return phone; } public void setPhone(String phone) { this.phone = phone; } public Person(String name, String phone) { this.name = name; this.phone = phone; } public Person(Integer id, String name, String phone,Integer amount) { super(); this.id = id; this.name = name; this.phone = phone; this.amount = amount; } public Person() { super(); } public Integer getAmount() { return amount; } public void setAmount(Integer amount) { this.amount = amount; } @Override public String toString() { return "Person [id=" + id + ", name=" + name + ", phone=" + phone + ", amount=" + amount + "]"; } }
九、DBOperateHelper.java 業務類源碼:
package com.example.service; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper; public class DBOperateHelper extends SQLiteOpenHelper { public DBOperateHelper(Context context) {//默認創建的數據庫文件保存在<包名>/database/ //第一個參數是上下文,第二個參數是數據庫名稱,第三個是游標工廠為null時使用 數據庫默認的游標工廠,第四個是數據庫版本號但是不能為0,一般大於0 super(context, "smallpig", null, 4); } /** * 數據庫每一次被創建時被調用 */ @Override public void onCreate(SQLiteDatabase sqldb) { sqldb.execSQL("create table person(personid integer primary key autoincrement,name varchar(20),phone varchar(12) null)"); } /** * 每一次數據庫版本號發生變動時觸發此方法 * 比如如果想往數據庫中再插入一些表、字段或者其他信息時通過修改數據庫版本號來觸發此方法 */ @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { //db.execSQL("alter table person add phone varchar(12) null");\ db.execSQL("alter table person add amount Integer null"); } }
十、PersonService.java 業務類源碼:
package com.example.service; import java.util.ArrayList; import java.util.List; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import com.example.domain.Person; public class PersonService { private DBOperateHelper dbOperateHelper; public PersonService(Context context) { this.dbOperateHelper = new DBOperateHelper(context); } /** * 保存記錄 * @param person */ public void save(Person person){ //得到數據庫實例,裡面封裝了數據庫操作方法 SQLiteDatabase sqldb = dbOperateHelper.getWritableDatabase(); //sqldb.execSQL("insert into person(name,phone) values('"+person.getName()+"','"+person.getPhone()+"')"); //利用占位符可以避免注入,但是注意數組參與與占位符對應的字段要一一對應 sqldb.execSQL("insert into person(name,phone,amount) values(?,?,?)",new Object[]{person.getName(),person.getPhone(),person.getAmount()}); //關閉數據庫 sqldb.close(); } /** * 刪除記錄 * @param id */ public void delete(Integer id){ SQLiteDatabase sqldb = dbOperateHelper.getWritableDatabase(); sqldb.execSQL("delete from person where personid=?",new Object[]{id}); sqldb.close(); } /** * 更新記錄 * @param person */ public void update(Person person){ SQLiteDatabase sqldb = dbOperateHelper.getWritableDatabase(); sqldb.execSQL("update person set name=?,phone=?,amount=? where personid=?",new Object[]{person.getName(),person.getPhone(),person.getAmount(),person.getId()}); sqldb.close(); } /** * 通過ID查詢記錄 * @param id * @return */ public Person find(Integer id){ /** * getWritableDatabase 與 getReadableDatabase 的區別: * getReadableDatabase會先返回getWritableDatabase(可寫),如果調用getWritableDatabase失敗 * 則才會調用getReadableDatabase後續方法,使數據庫只讀 * 當寫入的數據超過數據庫大小則調用getWritableDatabase會失敗 * 所以只讀時則可以使用此方法,其它情況(只要不是超過數據庫大小)也可以使用此方法 */ SQLiteDatabase sqldb = dbOperateHelper.getReadableDatabase(); Cursor cursor = sqldb.rawQuery("select * from person where personid=?", new String[]{String.valueOf(id)}); int personid; String name; String phone; int amount; Person person = null; if(cursor.moveToFirst()){ personid = cursor.getInt(cursor.getColumnIndex("personid")); name = cursor.getString(cursor.getColumnIndex("name")); phone = cursor.getString(cursor.getColumnIndex("phone")); amount = cursor.getInt(cursor.getColumnIndex("amount")); person = new Person(personid,name,phone,amount); } cursor.close(); return person; } /** * 返回指定長度記錄,limit 3,5,適用於分頁 * @param offset 起始 * @param maxResult 長度 * @return */ public List<Person> getScrollData(int offset,int maxResult){ SQLiteDatabase sqldb = dbOperateHelper.getReadableDatabase(); Cursor cursor = sqldb.rawQuery("select * from person order by personid asc limit ?,?", new String[]{String.valueOf(offset),String.valueOf(maxResult)}); int personid; String name; String phone; int amount; Person person = null; List<Person> persons = new ArrayList<Person>(); while(cursor.moveToNext()){ personid = cursor.getInt(cursor.getColumnIndex("personid")); name = cursor.getString(cursor.getColumnIndex("name")); phone = cursor.getString(cursor.getColumnIndex("phone")); amount = cursor.getInt(cursor.getColumnIndex("amount")); person = new Person(personid,name,phone,amount); persons.add(person); } cursor.close(); return persons; } /** * 返回cursor * @param offset 起始 * @param maxResult 長度 * @return */ public Cursor getCursorScrollData(int offset,int maxResult){ SQLiteDatabase sqldb = dbOperateHelper.getReadableDatabase(); Cursor cursor = sqldb.rawQuery("select personid as _id,name,phone,amount from person order by personid asc limit ?,?", new String[]{String.valueOf(offset),String.valueOf(maxResult)}); return cursor; } /** * 返回總記錄數 * @return */ public long getCount(){ SQLiteDatabase sqldb = dbOperateHelper.getReadableDatabase(); Cursor cursor = sqldb.rawQuery("select count(*) from person", null); //該查詢語句值返回一條語句 cursor.moveToFirst(); long result = cursor.getLong(0); cursor.close(); return result; } public void payment(){ SQLiteDatabase sqldb = dbOperateHelper.getWritableDatabase(); sqldb.beginTransaction();//開啟事務 try{ sqldb.execSQL("update person set amount = amount -10 where personid=1"); sqldb.execSQL("update person set amount = amount + 10 where personid=2"); sqldb.setTransactionSuccessful();//設置事務標志位true } finally { //結束事務:有兩種情況:commit\rollback,事務提交或者回滾是由事務的標識決定的 //事務為ture則提交,事務為flase則回滾,默認為false sqldb.endTransaction(); } } }
十一、OtherPersonService.java 業務類源碼:
package com.example.service; import java.util.ArrayList; import java.util.List; import com.example.domain.Person; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper; public class OtherPersonService { private DBOperateHelper dbOperateHelper; public OtherPersonService(Context context) { this.dbOperateHelper = new DBOperateHelper(context); } /** * 保存記錄 * @param person */ public void save(Person person){ //得到數據庫實例,裡面封裝了數據庫操作方法 SQLiteDatabase sqldb = dbOperateHelper.getWritableDatabase(); //sqldb.execSQL("insert into person(name,phone) values('"+person.getName()+"','"+person.getPhone()+"')"); //利用占位符可以避免注入,但是注意數組參與與占位符對應的字段要一一對應 //sqldb.execSQL("insert into person(name,phone) values(?,?)",new Object[]{person.getName(),person.getPhone()}); ContentValues values = new ContentValues(); values.put("name", person.getName()); values.put("phone", person.getPhone()); values.put("amount", person.getAmount()); //第一個參數是表名,第三個為字段值集合,第二個參數是空值字段,當第三個字段值集合為空時,系統會自動插入一條第二個參數為空的sql語句 //否則當第三個參數為空時,如果第二個參數也為空,那麼插入表就會找不到插入的字段信息,會報錯 sqldb.insert("person", "name", values ); //關閉數據庫 sqldb.close(); } /** * 刪除記錄 * @param id */ public void delete(Integer id){ SQLiteDatabase sqldb = dbOperateHelper.getWritableDatabase(); //sqldb.execSQL("delete from person where personid=?",new Object[]{id}); //第一個參數是表名,第二個是where後面的條件用占位符表示,第三個對應占位符為參數值 sqldb.delete("person", "personid=?", new String[]{Integer.toString(id)}); sqldb.close(); } /** * 更新記錄 * @param person */ public void update(Person person){ SQLiteDatabase sqldb = dbOperateHelper.getWritableDatabase(); //sqldb.execSQL("update person set name=?,phone=? where personid=?",new Object[]{person.getName(),person.getPhone(),person.getId()}); //第一個參數為表名,第二個是一個更新值集合,采用鍵值對的形式,每個更新的字段對應更新值 //第三個參數是where後面條件字段用占位符標識,第四個參數是對應where占位符的值 ContentValues values = new ContentValues(); values.put("name", person.getName()); values.put("phone", person.getPhone()); values.put("amount", person.getAmount()); sqldb.update("person", values , "personid=?", new String[]{person.getId().toString()}); sqldb.close(); } /** * 通過ID查詢記錄 * @param id * @return */ public Person find(Integer id){ /** * getWritableDatabase 與 getReadableDatabase 的區別: * getReadableDatabase會先返回getWritableDatabase(可寫),如果調用getWritableDatabase失敗 * 則才會調用getReadableDatabase後續方法,使數據庫只讀 * 當寫入的數據超過數據庫大小則調用getWritableDatabase會失敗 * 所以只讀時則可以使用此方法,其它情況(只要不是超過數據庫大小)也可以使用此方法 */ SQLiteDatabase sqldb = dbOperateHelper.getReadableDatabase(); //Cursor cursor = sqldb.rawQuery("select * from person where personid=?", new String[]{String.valueOf(id)}); //第一個參數是表名;第二個參數是查詢顯示的字段,null時默認查詢顯示所有字段; //第三個參數是where查詢條件占位符;第四個是占位符對應的值; //第五個參數是group by條件;第六個是having條件;第七個是order by條件 Cursor cursor = sqldb.query("person", null, "personid=?", new String[]{id.toString()}, null, null, null); int personid; String name; String phone; int amount; Person person = null; if(cursor.moveToFirst()){ personid = cursor.getInt(cursor.getColumnIndex("personid")); name = cursor.getString(cursor.getColumnIndex("name")); phone = cursor.getString(cursor.getColumnIndex("phone")); amount = cursor.getInt(cursor.getColumnIndex("amount")); person = new Person(personid,name,phone,amount); } cursor.close(); return person; } /** * 返回指定長度記錄,limit 3,5,適用於分頁 * @param offset 起始 * @param maxResult 長度 * @return */ public List<Person> getScrollData(int offset,int maxResult){ SQLiteDatabase sqldb = dbOperateHelper.getReadableDatabase(); //Cursor cursor = sqldb.rawQuery("select * from person order by personid asc limit ?,?", new String[]{String.valueOf(offset),String.valueOf(maxResult)}); //第一個參數是表名;第二個參數是查詢顯示的字段,null時默認查詢顯示所有字段; //第三個參數是where查詢條件占位符;第四個是占位符對應的值; //第五個參數是group by條件;第六個是having條件;第七個是order by條件 //第八個參數是limit ?,? 條件 Cursor cursor = sqldb.query("person", null, null, null, null, null, "personid",offset+","+maxResult); int personid; String name; String phone; int amount; Person person = null; List<Person> persons = new ArrayList<Person>(); while(cursor.moveToNext()){ personid = cursor.getInt(cursor.getColumnIndex("personid")); name = cursor.getString(cursor.getColumnIndex("name")); phone = cursor.getString(cursor.getColumnIndex("phone")); amount = cursor.getInt(cursor.getColumnIndex("amount")); person = new Person(personid,name,phone,amount); persons.add(person); } cursor.close(); return persons; } /** * 返回總記錄數 * @return */ public long getCount(){ SQLiteDatabase sqldb = dbOperateHelper.getReadableDatabase(); //Cursor cursor = sqldb.rawQuery("select count(*) from person", null); //第一個參數是表名;第二個參數是查詢顯示的字段,null時默認查詢顯示所有字段; //第三個參數是where查詢條件占位符;第四個是占位符對應的值; //第五個參數是group by條件;第六個是having條件;第七個是order by條件 Cursor cursor = sqldb.query("person", new String[]{"count(*)"}, null, null, null, null, null); //該查詢語句值返回一條語句 cursor.moveToFirst(); long result = cursor.getLong(0); cursor.close(); return result; } }
十二、PersonServiceTest.java 單元測試類源碼:
package com.example.test; import java.util.List; import com.example.domain.Person; import com.example.service.DBOperateHelper; import com.example.service.PersonService;import android.test.AndroidTestCase; import android.util.Log; public class PersonServiceTest extends AndroidTestCase { public void testCreateDB() throws Exception{ DBOperateHelper dbHelper = new DBOperateHelper(getContext()); dbHelper.getWritableDatabase(); } public void testSave() throws Exception{ PersonService ps = new PersonService(getContext()); for(int i=1;i<=100;i++){ Person person = new Person(); person.setName("我是"+i); person.setPhone(String.valueOf(Long.parseLong("18888888800")+i)); ps.save(person); Log.i("PersonService",person.toString()); } } public void testDelete() throws Exception{ PersonService ps = new PersonService(getContext()); ps.delete(10); } public void testUpdate() throws Exception{ PersonService ps = new PersonService(getContext()); ps.update(new Person(1,"xiaopang","18887654321",0)); } public void testFind() throws Exception{ PersonService ps = new PersonService(getContext()); Person person = ps.find(1); Log.i("PersonService", person.toString()); } public void testGetScrollData() throws Exception{ PersonService ps = new PersonService(getContext()); List<Person> persons = ps.getScrollData(3, 5); for(Person person:persons){ Log.i("PersonService",person.toString()); } } public void testGetCount() throws Exception{ PersonService ps = new PersonService(getContext()); Long count = ps.getCount(); Log.i("PersonService",count.toString()); } public void testUpdateAmount() throws Exception{ PersonService ps = new PersonService(getContext()); Person person1 = ps.find(1); Person person2 = ps.find(2); person1.setAmount(100); person2.setAmount(100); ps.update(person1); ps.update(person2); } public void testPayment() throws Exception{ PersonService ps = new PersonService(getContext()); ps.payment(); } }
十三、OtherPersonServiceTest 單元測試類源碼:
package com.example.test; import java.util.List; import com.example.domain.Person; import com.example.service.DBOperateHelper; import com.example.service.OtherPersonService; import android.test.AndroidTestCase; import android.util.Log; public class OtherPersonServiceTest extends AndroidTestCase { public void testCreateDB() throws Exception{ DBOperateHelper dbHelper = new DBOperateHelper(getContext()); dbHelper.getWritableDatabase(); } public void testSave() throws Exception{ OtherPersonService ps = new OtherPersonService(getContext()); for(int i=1;i<=100;i++){ Person person = new Person(); person.setName("我是"+i); person.setPhone(String.valueOf(Long.parseLong("18888888800")+i)); ps.save(person); Log.i("PersonService",person.toString()); } } public void testDelete() throws Exception{ OtherPersonService ps = new OtherPersonService(getContext()); ps.delete(10); } public void testUpdate() throws Exception{ OtherPersonService ps = new OtherPersonService(getContext()); ps.update(new Person(1,"xiaopang","18887654321",0)); } public void testFind() throws Exception{ OtherPersonService ps = new OtherPersonService(getContext()); Person person = ps.find(1); Log.i("PersonService", person.toString()); } public void testGetScrollData() throws Exception{ OtherPersonService ps = new OtherPersonService(getContext()); List<Person> persons = ps.getScrollData(3, 5); for(Person person:persons){ Log.i("PersonService",person.toString()); } } public void testGetCount() throws Exception{ OtherPersonService ps = new OtherPersonService(getContext()); Long count = ps.getCount(); Log.i("PersonService",count.toString()); } }
十四、注意事項以及相關知識點:
1、掌握SQLite數據庫如何創建數據庫、建立表、維護字段等操作
繼承SQLiteOpenHelper類,構造函數調用父類構造函數創建數據庫,利用onCreate創建表,利用onUpgrade更新表字段信息
2、掌握SQLite數據庫如何增、刪、改、查以及分頁
取得SQLiteDatabase的實例,然後調用該實例的方法可以完成上述操作
SQLiteDataBase提供兩種操作上述功能的方式:一是直接調用execSQL書寫sql語句,另一種是通過insert、update、delete、query等方法來傳值來拼接sql,前一種適合熟練掌握sql 語句的
3、對需要數據同步的處理請添加事務處理,熟悉事務的處理方式
4、了解各個方法參數的意義以及傳值
5、掌握ListView顯示後台數據的使用方法
SimpleAdapter、SimpleCursorAdapter以及自定義適配器的使用,以及OnItemClickListener取值時各個適配器返回值的區別以及取值方法
6、多學、多記、多練、多思,加油!
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希望本文所述對大家Android程序設計有所幫助。
QQ是大家離不開的聊天工具,方便既實用,自從qq更新至6.0之後,側滑由原來的劃出後主面板縮小變成了左右平滑,在外觀上有了很大的提升,於是我就是嘗試理解下裡面的各種邏輯,
Android生命周期估計連初學者都再熟悉不過的東西了,但這裡我拋出幾個問題,或許大家以前沒有想過或者可能認識的有些錯誤。 一、當A啟動B時,A和B生命周期方法執行的先後
一、問題描述使用百度地圖實現如圖所示應用,首先自動定位當前我起始位置(小圓點位置),並跟隨移動不斷自動定位我的當前位置百度Api不同版本使用會有些差異,本例中加入lib如
Android界面的坐標是以左上角為起始點,平行的為X軸,垂直的為Y軸,數值都是遞增的。如下圖所示: Android的Rect類是形成一個矩形的區域,區域