android开发-Listview中显示不同的视图布局

泡在网上的日子 / 文 发表于2012-08-02 21:41 次阅读 android

1.使用场景

  在重写ListView的BaseAdapter时,我们常常在getView()方法中复用convertView,以提高性能。convertViewItem为单一的同种类型布局时,能够回收并重用,但是多个Item布局类型不同时,convertView的回收和重用会出现问题。比如有些行为纯文本,有些行则是图文混排,这里纯文本行为一类布局,图文混排的行为第二类布局。单一类型的ListView很简单,下面着重介绍一下ListView包含多种类型视图布局的情形。

2.ListView包含不同Item的布局

  我们需要做这些工作:

  1)重写 getViewTypeCount() – 该方法返回多少个不同的布局

  2)重写 getItemViewType(int) – 根据position返回相应的Item

  3)根据view item的类型,在getView中创建正确的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(); 
    } 
    //每个convert view都会调用此方法,获得当前所需要的view样式 
    @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); 
      //无convertView,需要new出各个控件 
      if(convertView == null) 
      {  
        Log.e("convertView = ", " NULL"); 
        //按当前所需的样式,确定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,按样式,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; 
        } 
      } 
    //设置资源 
      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; 
    } 
  } 
  //各个布局的控件资源 
  class viewHolder1{ 
    CheckBox checkBox; 
    TextView textView; 
  } 
  class viewHolder2{ 
    TextView textView; 
  } 
  class viewHolder3{ 
    ImageView imageView; 
    TextView textView; 
  } 
}

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