Question

我创建了3个活动在First Activity中有两个按钮，当我点击startNotification它开始通知时并记下开始时间。当我们点击通知时，它打开secondActivity并发送注释当我现在去第二个活动然后从第三个活动转到第三个活动时，它会给出错误NullPointerException。

按钮点击

            NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            String MyText = "Reminder";
            Notification mNotification = new Notification(R.drawable.ic_launcher, MyText, System.currentTimeMillis() );
            int iUniqueId = (int) (System.currentTimeMillis() & 0xfffffff);
            String MyNotificationTitle = "Medicine!";
            String MyNotificationText  = "Don't forget to take your medicine!";
            MyIntent = new Intent(MainActivity.this,SecondActivity.class);
            MyIntent.putExtra("s1",System.currentTimeMillis());

            //PendingIntent StartIntent = PendingIntent.getActivity(getApplicationContext(),UNIQUE_INT_PER_CALL,MyIntent,0);

            PendingIntent contentIntent = PendingIntent.getActivity(context,iUniqueId,MyIntent,0);
            //A PendingIntent will be fired when the notification is clicked. The FLAG_CANCEL_CURRENT flag cancels the pendingintent

            mNotification.setLatestEventInfo(getApplicationContext(), MyNotificationTitle, MyNotificationText, contentIntent);
            mNotification.flags |= Notification.FLAG_AUTO_CANCEL;
            notificationManager.notify(0,   mNotification);

第二项活动

    Intent i=this.getIntent();
    if(i!=null)
    {
        **data=i.getStringExtra("summar");**

        if(data.equalsIgnoreCase("MainActivity"))
        {

            z=i.getExtras().getLong("s1");  
            int minutesZ = (int) ((z /(1000*60)) % 60);
            int minutesZ1 = (int) ((System.currentTimeMillis() /(1000*60)) % 60);
            Log.v("SecondTime",""+minutesZ);
            Log.v("CurrentTime",""+minutesZ1);
                x1=i.getExtras().getLong("s1");
            p=System.currentTimeMillis()-x1;
            int minutes = (int) ((p /(1000*60)) % 60);
            text1.setText(""+minutes);  
        }

        if(data.equalsIgnoreCase("ThirdActivity"))
        {
            //do something here
            Toast.makeText(SecondActivity.this,"hiii",2000).show();
        }
    }

第三项活动

 b1.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub

            Intent i=new Intent(ThirdActivity.this,SecondActivity.class);
            startActivity(i);
            i.putExtra("summar","ThirdActivity");
        }
    });

Answer 1

在你的第三个活动中，你正在启动意图，然后将额外的内容加入其中..而是尝试：

第三项活动

 b1.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View arg0) {
        // TODO Auto-generated method stub

        Intent i=new Intent(ThirdActivity.this,SecondActivity.class);
        i.putExtra("summar","ThirdActivity");
        startActivity(i);

    }
});

并且在您的第二个活动中，尝试在您的情况下进行额外检查（在意图中使用 hasExtra（）选项）：

Intent i=this.getIntent();
    if(i!=null)
    {
        if(i.hasExtra("summar"))        //---Might be useful if the intent doesn't have that extra
             data=i.getStringExtra("summar");

    if(data.equalsIgnoreCase("MainActivity"))
    {

        z=i.getExtras().getLong("s1");  
        int minutesZ = (int) ((z /(1000*60)) % 60);
        int minutesZ1 = (int) ((System.currentTimeMillis() /(1000*60)) % 60);
        Log.v("SecondTime",""+minutesZ);
        Log.v("CurrentTime",""+minutesZ1);
            x1=i.getExtras().getLong("s1");
        p=System.currentTimeMillis()-x1;
        int minutes = (int) ((p /(1000*60)) % 60);
        text1.setText(""+minutes);  
    }

    if(data.equalsIgnoreCase("ThirdActivity"))
    {
        //do something here
        Toast.makeText(SecondActivity.this,"hiii",2000).show();
    }
}

主要和空指针异常中的fata异常

1 个答案: