android - 应用程序在按下后退键时强制关闭

Question

我正在开发一个 VCard 应用程序。在这里我已经启动了默认联系人 Activity (地址簿)。

现在的申请流程是这样的，

• 用户启动应用程序。
• 已打开默认通讯录。
• 用户从列表中选择一个联系人，然后创建所选联系人的 Vcard。

现在，当用户在没有选择任何联系人的情况下按下后退按钮时，应用程序将被强制关闭。

我已经覆盖了 BackKeyPress() 事件，但它不起作用。该应用程序仍在强制关闭。

我贴出代码供引用，

    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Intent intent = new Intent(Intent.ACTION_PICK, ContactsContract.Contacts.CONTENT_URI);
        startActivityForResult(intent, 1);
        Log.d("In Oncreate", "Activity Result");
    }
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
         if (keyCode == KeyEvent.KEYCODE_BACK) {
         //preventing default implementation previous to android.os.Build.VERSION_CODES.ECLAIR
             Toast.makeText(getApplicationContext(), "Back Pressed", 5000).show();
             finish();
         return true;
         }
         return super.onKeyDown(keyCode, event);    
    }
    @Override
    public void onActivityResult(int reqCode, int resultCode, Intent data) {
      super.onActivityResult(reqCode, resultCode, data);

      switch (reqCode) {
        case (1) :
            counter = "Yes";
    Log.d("My Tag", data.getExtras().keySet().toString());
    name_selected = data.getExtras().getString("android.intent.extra.shortcut.NAME");
    Log.d("My Tag", name_selected));
    Intent i = new Intent(getApplicationContext(), BusinessCardActivity.class);
    i.putExtra("name", name_selected);
    i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    getApplicationContext().startActivity(i);
       }
    }
}

Logcat 错误:-

12-17 18:41:09.399: E/AndroidRuntime(23456): FATAL EXCEPTION: main
12-17 18:41:09.399: E/AndroidRuntime(23456): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=0, data=null} to activity {com.android.business/com.android.business.ReadContacts}: java.lang.NullPointerException
12-17 18:41:09.399: E/AndroidRuntime(23456):    at android.app.ActivityThread.deliverResults(ActivityThread.java:2536)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at android.app.ActivityThread.handleSendResult(ActivityThread.java:2578)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at android.app.ActivityThread.access$2000(ActivityThread.java:117)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:961)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at android.os.Looper.loop(Looper.java:123)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at android.app.ActivityThread.main(ActivityThread.java:3729)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at java.lang.reflect.Method.invokeNative(Native Method)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at java.lang.reflect.Method.invoke(Method.java:507)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:874)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:632)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at dalvik.system.NativeStart.main(Native Method)
12-17 18:41:09.399: E/AndroidRuntime(23456): Caused by: java.lang.NullPointerException
12-17 18:41:09.399: E/AndroidRuntime(23456):    at com.android.business.ReadContacts.onActivityResult(ReadContacts.java:133)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at android.app.Activity.dispatchActivityResult(Activity.java:3908)
12-17 18:41:09.399: E/AndroidRuntime(23456):    at android.app.ActivityThread.deliverResults(ActivityThread.java:2532)

在这里，用户应该从列表中选择一个联系人，但是如果用户在没有选择任何联系人的情况下按下返回按钮，应用程序将被强制关闭。

Answer 1

使用这个...

     @Override
public void onActivityResult(int reqCode, int resultCode, Intent data) {
  super.onActivityResult(reqCode, resultCode, data);

  switch (reqCode) {
    case 1:
    if(data!=null&&resultCode==RESULT_OK){


        counter = "Yes";
Log.d("My Tag", data.getExtras().keySet().toString());
name_selected = data.getExtras().getString("android.intent.extra.shortcut.NAME");
Log.d("My Tag", name_selected));
Intent i = new Intent(getApplicationContext(), BusinessCardActivity.class);
i.putExtra("name", name_selected);
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
getApplicationContext().startActivity(i);
   }
  }
}