Android检测是否安装了指定应用

检测是否安装了指定应用的方法如下：

private boolean isAvilible( Context context, String packageName )
    {
        final PackageManager packageManager = context.getPackageManager();
        // 获取所有已安装程序的包信息
        List<PackageInfo> pinfo = packageManager.getInstalledPackages(0);
        for ( int i = 0; i < pinfo.size(); i++ )
        {
            if(pinfo.get(i).packageName.equalsIgnoreCase(packageName))
                return true;
        }
        return false;
    }

然后检测并启动或安装：

if(isAvilible(MainActivity.this, "com.tencent.mm")){ 
           Intent i = new Intent(); 
           ComponentName cn = new ComponentName("com.tencent.mm", 
                            "com.tencent.mm.WeiXinActivity"); 
           i.setComponent(cn); 
           startActivityForResult(i, RESULT_OK);    
   } 
    //未安装，跳转至market下载该程序 
    else { 
                    Uri uri = Uri.parse("market://details?id=com.tencent.mm");
                    // 直接从指定网址下载
                    // Uri uri = Uri.parse("http://dldir1.qq.com/foxmail/weixin521android400.apk");
                    Intent it = new Intent(Intent.ACTION_VIEW, uri); 
                    startActivity(it); 
       }