編輯:關於Android編程
(1)程序說明
1)首先要添加文件創建,刪除,和寫入數據的權限
2)接著擴展fileobseerver,寫SDk文件監聽類。可以查看下文的文件監聽器源碼
3)如何啟動文件監控?
對於Activity來說通常在onResume()方法中調用startwatching()來啟動文件監控。
在onPause()方法中調用stopwatching()來取消文件監控。
(2)布局文件
(3)文件監聽器源碼:
1)擴展的Fileobserver,實現文件或者文件夾的監聽
package com.liuzuyi.fileobserver; import android.os.FileObserver; import android.util.Log; public class SDCardListener extends FileObserver { public SDCardListener(String path) { super(path); } public void onEvent(int event, String path) { switch (event) { case FileObserver.CREATE : Log.d("creat", "filename"+path); break; case FileObserver.ALL_EVENTS : Log.d("all", "filename"+path); break; } } }
2)主程序代碼
package com.liuzuyi.fileobserver; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.InputStream; import java.io.OutputStream; import android.app.Activity; import android.os.Bundle; import android.os.Environment; import android.util.Log; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; import android.widget.Toast; public class MainActivity extends Activity { private EditText filename; private EditText content; private TextView textcontent; private static final String TAG ="simplefile"; SDCardListener myfileListener = new SDCardListener("/sdcard"); public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); filename =(EditText)findViewById(R.id.filename); content =(EditText)findViewById(R.id.content); textcontent =(TextView)findViewById(R.id.textcontent); Button savebutton =(Button)this.findViewById(R.id.savebutton); Button viewbutton =(Button)this.findViewById(R.id.readbutton); savebutton.setOnClickListener(listener); viewbutton.setOnClickListener(listener); } public void onResume() { super.onResume(); myfileListener.startWatching(); } public void onPause() { super.onPause(); myfileListener.stopWatching(); } private View.OnClickListener listener = new OnClickListener() { public void onClick(View v) { Button button =(Button)v; String namestr =filename.getText().toString().trim(); String contentStr =content.getText().toString(); switch ( button.getId() ) { case R.id.savebutton: String res ="success"; try { if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) { FileOutputStream outstream = new FileOutputStream("/sdcard/"+namestr+".txt"); outstream.write(contentStr.getBytes() ); outstream.close(); } else return ; } catch (Exception e) { res= "failure"; e.printStackTrace(); } Toast.makeText(MainActivity.this, res ,Toast.LENGTH_LONG).show(); Log.i(TAG, namestr); Log.i(TAG, contentStr); break; case R.id.readbutton: String resid_v ="success"; String contentst = null; try { if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) { File SDCardDir=Environment.getExternalStorageDirectory(); File saveFile = new File(SDCardDir,namestr+".txt"); FileInputStream instream = new FileInputStream(saveFile); ByteArrayOutputStream Ostream = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len = -1; while( (len = instream.read(buffer)) != -1 ) { Ostream.write(buffer,0,len); } contentst = Ostream.toString(); Ostream.close(); instream.close(); } else { Toast.makeText(MainActivity.this, "SD卡不存在", Toast.LENGTH_LONG).show(); } } catch (Exception e) { resid_v ="faile"; e.printStackTrace(); } textcontent.setText( contentst); Log.i(TAG, contentst); Toast.makeText(MainActivity.this, resid_v,Toast.LENGTH_LONG).show(); Log.i(TAG,namestr); break; } } }; }
ScrollView滾動視圖ScrollView是繼承於FrameLayout,也是一個顯示容器,由於手機屏幕是有限的,當需要組件安排多組信息的時候,ScrollView
首先設置兩個布局文件,一個布局文件進行輸入數據,獲取加法運算;另一個布局文件進行顯示最終結果。Activity1啟動Activity2,並傳遞計算結果值給Activity
1. 清單文件AndroidManifest.xml1.1. 清單文件的作用每個Android應用都需要一個名為AndroidManifest.xml的程序清單文件,這個
本博客涉及的內容有:多線程並發的性能問題,介紹了AsyncTask,HandlerThread,IntentService與ThreadPool分別適合的使用場景以及各自