app打开另一个app

try {
    PackageManager packageManager = getPackageManager();
    Intent intent=new Intent();
    intent = packageManager.getLaunchIntentForPackage("com.tencent.mm");
    startActivity(intent);
} catch (Exception e) {
    e.printStackTrace();
    Intent viewIntent = new
    Intent("android.intent.action.VIEW",Uri.parse("http://weixin.qq.com/"));
    startActivity(viewIntent);
}

如果安装了微信则直接打开，否则启动游览器去官网下载