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 Android教程網 >> Android技術 >> 關於Android編程 >> Android Listview中顯示不同的視圖布局詳解及實例代碼

Android Listview中顯示不同的視圖布局詳解及實例代碼

編輯:關於Android編程

Android Listview中顯示不同的視圖布局

1. 使用場景

在重寫ListView的BaseAdapter時,我們常常在getView()方法中復用convertView,以提高性能。convertView在Item為單一的同種類型布局時,能夠回收並重用,但是多個Item布局類型不同時,convertView的回收和重用會出現問題。比如有些行為純文本,有些行則是圖文混排,這裡純文本行為一類布局,圖文混排的行為第二類布局。單一類型的ListView很簡單,下面著重介紹一下ListView包含多種類型視圖布局的情形。

2.ListView包含不同Item的布局

我們需要做這些工作:

  1)重寫 getViewTypeCount() – 該方法返回多少個不同的布局
  2)重寫 getItemViewType(int) – 根據position返回相應的Item
  3)根據view item的類型,在getView中創建正確的convertView

3.案例

import java.util.ArrayList; 

import android.app.Activity; 
import android.content.Context; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.CheckBox; 
import android.widget.ImageView; 
import android.widget.LinearLayout; 
import android.widget.ListView; 
import android.widget.TextView; 

public class listViewTest extends Activity { 
/** Called when the activity is first created. */
  ListView listView; 
  MyAdapter listAdapter; 
  ArrayList<String> listString; 

  @Override 
  public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
    listView = (ListView)this.findViewById(R.id.listview); 
    listString = new ArrayList<String>(); 
    for(int i = 0 ; i < 100 ; i++) 
    { 
      listString.add(Integer.toString(i)); 
    } 
    listAdapter = new MyAdapter(this); 
    listView.setAdapter(listAdapter); 
  } 

  class MyAdapter extends BaseAdapter{ 
    Context mContext; 
    LinearLayout linearLayout = null; 
    LayoutInflater inflater; 
    TextView tex; 
    final int VIEW_TYPE = 3; 
    final int TYPE_1 = 0; 
    final int TYPE_2 = 1; 
    final int TYPE_3 = 2; 

    public MyAdapter(Context context) { 
      // TODO Auto-generated constructor stub 
      mContext = context; 
      inflater = LayoutInflater.from(mContext); 
    } 

    @Override 
    public int getCount() { 
      // TODO Auto-generated method stub 
      return listString.size(); 
    } 

    //每個convert view都會調用此方法,獲得當前所需要的view樣式 
    @Override 
    public int getItemViewType(int position) { 
      // TODO Auto-generated method stub 
      int p = position%6; 
      if(p == 0) 
        return TYPE_1; 
      else if(p < 3) 
        return TYPE_2; 
      else if(p < 6) 
        return TYPE_3; 
      else
        return TYPE_1; 
    } 

    @Override 
    public int getViewTypeCount() { 
      // TODO Auto-generated method stub 
      return 3; 
    } 

    @Override 
    public Object getItem(int arg0) { 
      // TODO Auto-generated method stub 
      return listString.get(arg0); 
    } 

    @Override 
    public long getItemId(int position) { 
      // TODO Auto-generated method stub 
      return position; 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
      // TODO Auto-generated method stub 
      viewHolder1 holder1 = null; 
      viewHolder2 holder2 = null; 
      viewHolder3 holder3 = null; 
      int type = getItemViewType(position); 

      //無convertView,需要new出各個控件 
      if(convertView == null) 
      { 
        Log.e("convertView = ", " NULL"); 

        //按當前所需的樣式,確定new的布局 
        switch(type) 
        { 
        case TYPE_1: 
          convertView = inflater.inflate(R.layout.listitem1, parent, false); 
          holder1 = new viewHolder1(); 
          holder1.textView = (TextView)convertView.findViewById(R.id.textview1); 
          holder1.checkBox = (CheckBox)convertView.findViewById(R.id.checkbox); 
          Log.e("convertView = ", "NULL TYPE_1"); 
          convertView.setTag(holder1); 
          break; 
        case TYPE_2: 
          convertView = inflater.inflate(R.layout.listitem2, parent, false); 
          holder2 = new viewHolder2(); 
          holder2.textView = (TextView)convertView.findViewById(R.id.textview2); 
          Log.e("convertView = ", "NULL TYPE_2"); 
          convertView.setTag(holder2); 
          break; 
        case TYPE_3: 
          convertView = inflater.inflate(R.layout.listitem3, parent, false); 
          holder3 = new viewHolder3(); 
          holder3.textView = (TextView)convertView.findViewById(R.id.textview3); 
          holder3.imageView = (ImageView)convertView.findViewById(R.id.imageview); 
          Log.e("convertView = ", "NULL TYPE_3"); 
          convertView.setTag(holder3); 
          break; 
        } 
      }else{ 
        //有convertView,按樣式,取得不用的布局 
        switch(type) 
        { 
        case TYPE_1: 
          holder1 = (viewHolder1) convertView.getTag(); 
          Log.e("convertView !!!!!!= ", "NULL TYPE_1"); 
          break; 
        case TYPE_2: 
          holder2 = (viewHolder2) convertView.getTag(); 
          Log.e("convertView !!!!!!= ", "NULL TYPE_2"); 
          break; 
        case TYPE_3: 
          holder3 = (viewHolder3) convertView.getTag(); 
          Log.e("convertView !!!!!!= ", "NULL TYPE_3"); 
          break; 
        } 
      } 

    //設置資源 
      switch(type) 
      { 
        case TYPE_1: 
          holder1.textView.setText(Integer.toString(position)); 
          holder1.checkBox.setChecked(true); 
          break; 
        case TYPE_2: 
          holder2.textView.setText(Integer.toString(position)); 
          break; 
        case TYPE_3: 
          holder3.textView.setText(Integer.toString(position)); 
          holder3.imageView.setBackgroundResource(R.drawable.icon); 
          break; 
      } 

      return convertView; 
    } 
  } 

  //各個布局的控件資源 
  class viewHolder1{ 
    CheckBox checkBox; 
    TextView textView; 
  } 

  class viewHolder2{ 
    TextView textView; 
  } 

  class viewHolder3{ 
    ImageView imageView; 
    TextView textView; 
  } 
}

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