Kontrollieren Sie die Rückseite „Knopf“ in android

Question

Ich will zurück, um den Text Datenwert von Sub-Aktivität zu erhalten. Und alles ist in Ordnung. Aber wenn die Teilaktivität geöffnet wurde, dann klicke ich einfach zurück „Knopf“ am Telefon, es einen Ausnahmefehler werfen. Ich fand auf der Android NotePad Lebenszyklussteuerung toturial aber es ist schwer zu verstehen. Kann mir jemand helfen? Dies ist mein Code:

public class SBooks extends ListActivity {
private String title_raw;
private SBooksDbAdapter mDbHelper;  
private static final int ACTIVITY_SEARCH = 0;   

private static final int SEARCH_ID = Menu.FIRST;     

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.sbooks_list);       
    mDbHelper = new SBooksDbAdapter(this);
    mDbHelper.open();                    

}

// Create Menu Option
@Override
public boolean onCreateOptionsMenu(Menu menu) {        
    boolean result = super.onCreateOptionsMenu(menu);
    menu.add(0, SEARCH_ID, 0, R.string.menu_search);            
    return result;      
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch(item.getItemId()){
    case SEARCH_ID:
        Intent intent = new Intent(this, SBooksSearch.class);
        startActivityForResult(intent, ACTIVITY_SEARCH);            

    return super.onOptionsItemSelected(item);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent intent){
    super.onActivityResult(requestCode, resultCode, intent);
        switch(requestCode){
        case ACTIVITY_SEARCH:
            Bundle bundle = intent.getExtras();
            title_raw = bundle.getString(SBooksDbAdapter.KEY_TITLE_RAW);
            if(title_raw!=null){
                Cursor cursor = mDbHelper.searchData(title_raw);
                String[] from = new String[]{ SBooksDbAdapter.KEY_ROWID,
                        SBooksDbAdapter.KEY_TITLE, SBooksDbAdapter.KEY_LYRICS };
                int[] to = new int[]{ R.id.id, R.id.title, R.id.lyrics };
                SimpleCursorAdapter adapter = 
                    new SimpleCursorAdapter(this, R.layout.sbooks_row, cursor, from, to );
                setListAdapter(adapter);

        }

    }   
}

}

Das ist mein Subaktivität:

public class SBooksSearch extends Activity {
private EditText mTextSearch;
private Button searchButton;
private SBooksDbAdapter mDbHelper;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);     
    setContentView(R.layout.sbooks_search); 

    mTextSearch = (EditText)findViewById(R.id.text_search);     
    searchButton = (Button)findViewById(R.id.btn_search);       

    searchButton.setOnClickListener(new View.OnClickListener(){
        public void onClick(View v){                
            Intent intent = new Intent();
            intent.putExtra(SBooksDbAdapter.KEY_TITLE_RAW, mTextSearch.getText().toString());               
            setResult(RESULT_OK, intent);
            finish();

        }
    });
}   

@Override
protected void onSaveInstanceState(Bundle outState){
    super.onSaveInstanceState(outState);

}
@Override
protected void onPause(){
    super.onPause();
    checkState();

}
@Override
protected void onResume(){
    super.onResume();       
}


private void checkState() {     

} }

Dies ist Logcat:

08-12 18:44:39.211: WARN/InputManagerService(581): Starting input on non-focused client com.android.internal.view.IInputMethodClient$Stub$Proxy@43719140 (uid=10004 pid=623)
08-12 18:44:39.510: INFO/ActivityManager(581): Displayed activity com.original.sbooks/.SBooks: 4934 ms
08-12 18:44:40.821: WARN/KeyCharacterMap(730): No keyboard for id 0
08-12 18:44:40.821: WARN/KeyCharacterMap(730): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
08-12 18:44:41.412: INFO/ARMAssembler(581): generated scanline__00000177:03515104_00001A01_00000000 [ 64 ipp] (89 ins) at [0x297608:0x29776c] in 952924 ns
08-12 18:44:41.520: INFO/ARMAssembler(581): generated scanline__00000177:03515104_00000A01_00000000 [ 46 ipp] (70 ins) at [0x297798:0x2978b0] in 517061 ns
08-12 18:44:42.171: INFO/ActivityManager(581): Starting activity: Intent { comp={com.original.sbooks/com.original.sbooks.SBooksSearch} }
08-12 18:44:52.196: WARN/ActivityManager(581): Launch timeout has expired, giving up wake lock!
08-12 18:44:52.279: WARN/ActivityManager(581): Activity idle timeout for HistoryRecord{436bfc80 {com.original.sbooks/com.original.sbooks.SBooksSearch}}
08-12 18:44:57.350: DEBUG/dalvikvm(620): GC freed 4103 objects / 231808 bytes in 75ms
08-12 18:45:05.130: DEBUG/dalvikvm(649): GC freed 2604 objects / 150112 bytes in 88ms
08-12 18:45:10.120: DEBUG/dalvikvm(623): GC freed 2750 objects / 149592 bytes in 71ms
08-12 18:45:11.920: INFO/ActivityManager(581): Displayed activity com.original.sbooks/.SBooksSearch: 29748 ms
08-12 18:45:17.263: WARN/ActivityManager(581): Activity pause timeout for HistoryRecord{436bfc80 {com.original.sbooks/com.original.sbooks.SBooksSearch}}
08-12 18:45:26.762: WARN/ActivityManager(581): Launch timeout has expired, giving up wake lock!
08-12 18:45:27.272: WARN/ActivityManager(581): Activity idle timeout for HistoryRecord{435a7760 {com.original.sbooks/com.original.sbooks.SBooks}}
08-12 18:46:04.905: DEBUG/AndroidRuntime(730): Shutting down VM
08-12 18:46:04.905: WARN/dalvikvm(730): threadid=3: thread exiting with uncaught exception (group=0x4000fe70)
08-12 18:46:04.905: ERROR/AndroidRuntime(730): Uncaught handler: thread main exiting due to uncaught exception
08-12 18:46:04.991: ERROR/AndroidRuntime(730): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=0, result=0, data=null} to activity {com.original.sbooks/com.original.sbooks.SBooks}: java.lang.NullPointerException
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at android.app.ActivityThread.deliverResults(ActivityThread.java:3005)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at android.app.ActivityThread.handleSendResult(ActivityThread.java:3047)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at android.app.ActivityThread.access$2300(ActivityThread.java:112)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1721)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at android.os.Looper.loop(Looper.java:123)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at android.app.ActivityThread.main(ActivityThread.java:3948)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at java.lang.reflect.Method.invokeNative(Native Method)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at java.lang.reflect.Method.invoke(Method.java:521)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:782)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:540)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at dalvik.system.NativeStart.main(Native Method)
08-12 18:46:04.991: ERROR/AndroidRuntime(730): Caused by: java.lang.NullPointerException
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at com.original.sbooks.SBooks.onActivityResult(SBooks.java:111)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at android.app.Activity.dispatchActivityResult(Activity.java:3595)
08-12 18:46:04.991: ERROR/AndroidRuntime(730):     at android.app.ActivityThread.deliverResults(ActivityThread.java:3001)

Answer 1

Ich denke, Nate über die NPE bei intent.getExtras korrekt ist ().

Sie sollten den Wert Ihres Ergebniscode werden überprüft, bevor Sie etwas tun. Vielleicht haben Sie auch sicher, dass intent.hasExtra (SBooksDbAdapter.KEY_TITLE_RAW) überprüfen wollen machen, bevor Sie diesen Wert erhalten. So etwas wie folgt aus:

switch(requestCode){
case ACTIVITY_SEARCH:
    if (resultCode == RESULT_OK && intent.hasExtra(SBooksDbAdapter.KEY_TITLE_RAW)) {
        title_raw = intent.getStringExtra(SBooksDbAdapter.KEY_TITLE_RAW);
        ... do all that other stuff ...
    }
}

Answer 2

Versuchen Sie es in einigen Protokollierung in die onActivityResult (...) Methode Ihrer Haupttätigkeit setzen. Die Schaltfläche „Zurück“ aus der Teilaktivität können Ihnen einen Ergebniscode von RESULT_CANCELED werden geben, und die Absicht, in diesem Fall null sein. So erhalten Sie eine NPE an

erhalten

Bundle Bündel = intent.getExtras ();