Android开发之一个未解决的bug

使用Activity之间传递数据的时候，出现了一个bug，但是没有找到哪里出错了。

把代码和log都记录下来，以后研究

代码：

MainActivity.class

 1 package com.example.caradviser;
 2
 3 import java.util.ArrayList;
 4 import java.util.List;
 5
 6 import android.app.Activity;
 7 import android.content.Intent;
 8 import android.net.Uri;
 9 import android.os.Bundle;
10 import android.util.Log;
11 import android.view.View;
12 import android.view.Window;
13 import android.widget.Spinner;
14 import android.widget.TextView;
15 import android.widget.Toast;
16
17 public class MainActivity extends Activity {
18
19     private static final String TAG = "com.example.caradviser";
20     TextView showBackText;
21
22     @Override
23     protected void onCreate(Bundle savedInstanceState) {
24         super.onCreate(savedInstanceState);
25         requestWindowFeature(Window.FEATURE_NO_TITLE);
26         setContentView(R.layout.activity_main);
27         showBackText=(TextView) findViewById(R.id.backMainActivity);
28     }
29
30     @Override
31     protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
32         super.onActivityResult(requestCode, resultCode, intent);
33
34         switch (requestCode) {
35         case 123123:
36             if (resultCode==RESULT_OK) {
37                 if (intent==null||"".equals(intent)) {
38                     Toast.makeText(MainActivity.this, "获取到的数据为空", Toast.LENGTH_SHORT).show();
39                 }else {
40                     String getData = intent.getStringExtra("data_return");
41                     showBackText.setText(intent.getStringExtra("data_return"));
42                 }
43             }
44             break;
45
46         default:
47             break;
48         }
49     }
50
51
52     public void toAnotherActivity3(View v){
53         String data ="Hello,这是传递的数据";
54         Intent intent = new Intent(MainActivity.this,ThreeActivity.class);
55         intent.putExtra("haha", data);
56         startActivityForResult(intent, 123123);
57     }
58 }

ThreeActivity.class

 1 package com.example.caradviser;
 2
 3 import android.app.Activity;
 4 import android.content.Intent;
 5 import android.os.Bundle;
 6 import android.text.TextUtils;
 7 import android.view.View;
 8 import android.view.View.OnClickListener;
 9 import android.view.Window;
10 import android.widget.Button;
11 import android.widget.TextView;
12 import android.widget.Toast;
13
14 public class ThreeActivity extends Activity {
15
16     private Button backToMainActivity;
17     private String data;
18     private TextView textView;
19
20     @Override
21     protected void onCreate(Bundle savedInstanceState) {
22         // TODO Auto-generated method stub
23         super.onCreate(savedInstanceState);
24         requestWindowFeature(Window.FEATURE_NO_TITLE);
25         setContentView(R.layout.three_layout);
26
27         Intent intent = getIntent();
28         data = intent.getStringExtra("haha");
29
30         textView = (TextView) findViewById(R.id.showText);
31
32         if (TextUtils.isEmpty(data)) {
33             Toast.makeText(ThreeActivity.this, "没有接收到其他activity的数据", Toast.LENGTH_SHORT).show();
34         }else {
35             textView.setText(data);
36         }
37
38
39         backToMainActivity = (Button) findViewById(R.id.backMainActivity);
40         backToMainActivity.setOnClickListener(new OnClickListener() {
41
42             @Override
43             public void onClick(View v) {
44                 // TODO Auto-generated method stub
45                 Intent intent = new Intent();
46                 String data3= "将要返回到MainActivity";
47                 intent.putExtra("data_return", data3);
48                 setResult(RESULT_OK,intent);
49                 finish();
50             }
51         });
52     }
53
54 }

Log

 1 10-12 16:22:02.304: E/AndroidRuntime(16265): FATAL EXCEPTION: main
 2 10-12 16:22:02.304: E/AndroidRuntime(16265): Process: com.example.caradviser, PID: 16265
 3 10-12 16:22:02.304: E/AndroidRuntime(16265): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=123123, result=-1, data=Intent { (has extras) }} to activity {com.example.caradviser/com.example.caradviser.MainActivity}: java.lang.NullPointerException
 4 10-12 16:22:02.304: E/AndroidRuntime(16265):     at android.app.ActivityThread.deliverResults(ActivityThread.java:3375)
 5 10-12 16:22:02.304: E/AndroidRuntime(16265):     at android.app.ActivityThread.handleSendResult(ActivityThread.java:3418)
 6 10-12 16:22:02.304: E/AndroidRuntime(16265):     at android.app.ActivityThread.access$1300(ActivityThread.java:141)
 7 10-12 16:22:02.304: E/AndroidRuntime(16265):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1261)
 8 10-12 16:22:02.304: E/AndroidRuntime(16265):     at android.os.Handler.dispatchMessage(Handler.java:102)
 9 10-12 16:22:02.304: E/AndroidRuntime(16265):     at android.os.Looper.loop(Looper.java:136)
10 10-12 16:22:02.304: E/AndroidRuntime(16265):     at android.app.ActivityThread.main(ActivityThread.java:5072)
11 10-12 16:22:02.304: E/AndroidRuntime(16265):     at java.lang.reflect.Method.invokeNative(Native Method)
12 10-12 16:22:02.304: E/AndroidRuntime(16265):     at java.lang.reflect.Method.invoke(Method.java:515)
13 10-12 16:22:02.304: E/AndroidRuntime(16265):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
14 10-12 16:22:02.304: E/AndroidRuntime(16265):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
15 10-12 16:22:02.304: E/AndroidRuntime(16265):     at dalvik.system.NativeStart.main(Native Method)
16 10-12 16:22:02.304: E/AndroidRuntime(16265): Caused by: java.lang.NullPointerException
17 10-12 16:22:02.304: E/AndroidRuntime(16265):     at com.example.caradviser.MainActivity.onActivityResult(MainActivity.java:42)
18 10-12 16:22:02.304: E/AndroidRuntime(16265):     at android.app.Activity.dispatchActivityResult(Activity.java:5441)
19 10-12 16:22:02.304: E/AndroidRuntime(16265):     at android.app.ActivityThread.deliverResults(ActivityThread.java:3371)
20 10-12 16:22:02.304: E/AndroidRuntime(16265):     ... 11 more

具体什么原因造成的，目前我还无法确定，等待能力提高以后，回头看看这个问题。