java - 验证 Intent 是否进行有效的 Activity

Question

public void action(View view){
    Intent intent = new Intent(Settings.ACTION_DEVICE_INFO_SETTINGS);
    if(intent!=null) //here is my problem, it return true always
     {startActivity(intent);}
     else{k++;
         Context context = getApplicationContext();
         CharSequence mesajText = "Failed To Open! " + k;
         int duration = 3;
         Toast screen_message = Toast.makeText(context,mesajText,duration);
         screen_message.show();
         }
}

如何验证我的“Intent ”是否具有有效的 Activity (打开时有效)或无效的 Activity (打开时应用程序崩溃)？

Answer 1

if(intent!=null) 将始终评估为 true，因为您在 if 条件 之前初始化 Intent 。如果您想检查是否可以处理Intent，请使用resolveActivity，如下所示:

Intent intent = new Intent(Settings.ACTION_DEVICE_INFO_SETTINGS);
PackageManager packageManager = getPackageManager();
if (intent.resolveActivity(packageManager) != null) {
    startActivity(intent);
} else{
   k++;
   CharSequence mesajText = "Failed To Open! " + k;
   int duration = 3;
   Toast screen_message = Toast.makeText(this,mesajText,duration);
   screen_message.show();
}