有时需对已安装的应用进行管理 ， 这里我简单的写了获取应用程序列表。
代码如下：
package com.lml.applicationtest;

import java.util.List;

import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.PixelFormat;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends Activity {

private ListView lv;
private List<PackageInfo> pakageinfos;
private PackageManager pm;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lv = (ListView) findViewById(R.id.list);
makeList();
}

private void makeList() {
pm = getPackageManager();
pakageinfos = pm.getInstalledPackages(PackageManager.GET_UNINSTALLED_PACKAGES);
lv.setAdapter(new MyAdapter(this));
}

private class MyAdapter extends BaseAdapter {

private Context context;// 用于接收传递过来的Context对象

public MyAdapter(Context context) {
this.context = context;
}

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

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

@Override
public long getItemId(int arg0) {
// TODO Auto-generated method stub
return arg0;
}

@Override
public View getView(int arg0, View arg1, ViewGroup arg2) {
// TODO Auto-generated method stub
PackageInfo info = pakageinfos.get(arg0);
View view = View.inflate(context, R.layout.item, null);
Drawable drawable=info.applicationInfo.loadIcon(pm);

((ImageView) view.findViewById(R.id.iv)).setImageDrawable(zoomDrawable(drawable,50,50));
((TextView) view.findViewById(R.id.tv)).setText(info.applicationInfo.loadLabel(pm));
return view;
}

}

private Bitmap drawableToBitmap(Drawable drawable)// drawable 转换成bitmap
{
int width = drawable.getIntrinsicWidth(); // 取drawable的长宽
int height = drawable.getIntrinsicHeight();
Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
: Bitmap.Config.RGB_565; // 取drawable的颜色格式
Bitmap bitmap = Bitmap.createBitmap(width, height, config); // 建立对应bitmap
Canvas canvas = new Canvas(bitmap); // 建立对应bitmap的画布
drawable.setBounds(0, 0, width, height);
drawable.draw(canvas); // 把drawable内容画到画布中
return bitmap;
}

private Drawable zoomDrawable(Drawable drawable, int w, int h)
         {
                   int width = drawable.getIntrinsicWidth();
                   int height= drawable.getIntrinsicHeight();
                   Bitmap oldbmp = drawableToBitmap(drawable);// drawable转换成bitmap
                   Matrix matrix = new Matrix();   // 创建操作图片用的Matrix对象
                   float scaleWidth = ((float)w / width);   // 计算缩放比例
                   float scaleHeight = ((float)h / height);
                   matrix.postScale(scaleWidth, scaleHeight);         // 设置缩放比例
                   Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height, matrix, true);       // 建立新的bitmap，其内容是对原bitmap的缩放后的图
                   return new BitmapDrawable(getResources() ,newbmp);       // 把bitmap转换成drawable并返回
         }

}