android 获取已安装程序列表

public void btn1Click(View v){
        String str = null;        
        PackageManager manager = this.getPackageManager();
        List<PackageInfo> pkgList = manager.getInstalledPackages(0);
        for (int i = 0; i < pkgList.size(); i++) {
            PackageInfo pI = pkgList.get(i);
            str = str + "\n" + pI.packageName;
        }
        TextView tv1 = (TextView)findViewById(R.id.textView1);
        tv1.setMovementMethod(ScrollingMovementMethod.getInstance()); 
        tv1.setText(str);
    }