我＆＃39; MainActivity如下：
public class MainActivity extends AppCompatActivity {
DatabaseHelper myDb;
TextView textView;
Button button;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
myDb =new DatabaseHelper(this);
Cursor res= myDb.getAllData();
if(res.getCount()==0)
{
textView = (TextView)findViewById(R.id.textView);
textView.setText("No Reminders");
button = (Button)findViewById(R.id.button);
button.setText("Create a Reminder");
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) { //on click 2nd activity is called.
Intent myIntent = new Intent(MainActivity.this, Main2Activity.class);
//myIntent.putExtra("key", value); //Optional parameters
startActivity(myIntent);
}
});
return;
}
StringBuffer buffer=new StringBuffer();
while(res.moveToNext())
{
buffer.append("Id : " +res.getString(0)+"\n");
buffer.append("Event : " +res.getString(1)+"\n");
buffer.append("Location : " +res.getString(2)+"\n");
}
textView = (TextView)findViewById(R.id.textView);
textView.setText(buffer.toString());
}
}
我还有另一个名为main2activity的活动。但是当我在第一个活动中按下按钮时，应用程序崩溃并记录日志NullPointerException。 但这不是任何其他此类NullPointerException问题的重复。
因为当我仅运行第二个活动Main2Activity时，它不会给出此错误。但是当从mainActivity调用它时，它会给出错误。我无法理解为什么在按钮上设置监听器NullPointerException。
我的Main2Activity是：
public class Main2Activity extends AppCompatActivity {
private static final int PLACE_PICKER_REQUEST = 1;
private TextView mName;
private TextView mAddress;
private TextView mAttributions;
private GoogleApiClient mGoogleApiClient;
public TextView tv4;
private static final LatLngBounds BOUNDS_MOUNTAIN_VIEW = new LatLngBounds(
new LatLng(37.398160, -122.180831), new LatLng(37.430610, -121.972090));
private boolean flag = false;
DatabaseHelper myDb;
EditText newevent;
Button submit;
Button viewremainders;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = getIntent();
setContentView(R.layout.activity_main);
myDb =new DatabaseHelper(this);
newevent=(EditText)findViewById(R.id.newEvent);
submit=(Button)findViewById(R.id.submit);
viewremainders=(Button)findViewById(R.id.view);
Button pickerButton = (Button) findViewById(R.id.pickerButton);
tv4 = (TextView)findViewById(R.id.textView4);
pickerButton.setOnClickListener(new View.OnClickListener() { // <-- Error is here. (NullPointerException.)
@Override
public void onClick(View v) {
try {
PlacePicker.IntentBuilder intentBuilder =
new PlacePicker.IntentBuilder();
intentBuilder.setLatLngBounds(BOUNDS_MOUNTAIN_VIEW);
Intent intent = intentBuilder.build(Main2Activity.this);
startActivityForResult(intent, PLACE_PICKER_REQUEST);
} catch (GooglePlayServicesRepairableException
| GooglePlayServicesNotAvailableException e) {
e.printStackTrace();
}
}
});
AddData();
viewremainders();
}
我在这里提到了评论中发生错误的位置。我还有其他方法，但只包括必要的部分。
提前致谢！
修改： 经度：
08-18 21:48:05.421 29655-29655/com.example.kaushal28.locationbasedreminder E/test: Exception
08-18 21:48:05.424 29655-29655/com.example.kaushal28.locationbasedreminder E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.kaushal28.locationbasedreminder/com.example.kaushal28.locationbasedreminder.Main2Activity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2306)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
at android.app.ActivityThread.access$600(ActivityThread.java:156)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1340)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:153)
at android.app.ActivityThread.main(ActivityThread.java:5299)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.kaushal28.locationbasedreminder.Main2Activity.onCreate(Main2Activity.java:85)
at android.app.Activity.performCreate(Activity.java:5182)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1081)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
at android.app.ActivityThread.access$600(ActivityThread.java:156)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1340)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:153)
at android.app.ActivityThread.main(ActivityThread.java:5299)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
您在两个活动中设置相同的布局。确保并添加正确的布局。
setContentView(R.layout.activity_main);
public class Main2Activity extends AppCompatActivity {
.
.
.
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = getIntent();
setContentView(R.layout.activity_main); // here is issue same layout is used for both activity
}
}