Android onBackPressed() 里调用 setResult(RESULT_OK) 无效

当从第一个Activity使用startActivityForResult启动第二个SecActivity,在SecActivity的onBackPressed()方法内调用setResult(RESULT_OK)无法正确返回结果。解决办法详述。

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   从第一个Activity startActivityForResult 到第二个SecActivity ,在onBackPressed()里调用setResult(RESULT_OK),不能返回正确的值,如下:



 第一个Activity

public class MainActivity extends AppCompatActivity {

    public static final  int REQUEST_CODE = 1024 ;
    private TextView textView ;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = (TextView)findViewById(R.id.tv1);
      /*  getWindow().addFlags(WindowManager.LayoutParams.FLAG_SECURE);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);*/

        textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this,SecActivity.class);
                startActivityForResult(intent,REQUEST_CODE);
            }
        });

    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode)
        {
            case REQUEST_CODE :
                if(resultCode == RESULT_OK)
                {
                    textView .setText("回调成功");
                }
                break;
        }
    }
}
secActivity

public class SecActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sec);
    }

    @Override
    public void onBackPressed() {
        super.onBackPressed();
        setResult(RESULT_OK);

    }

点击返回键,没有正确得到回调!这是为何?因为OnBackPressed() 会默认设置setResult(RESULT_CANCELED);

解决方案:

@Override
    public void onBackPressed() {

        setResult(RESULT_OK);
        super.onBackPressed();
    }




/* * Copyright (C) 2018 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.android.settings.localepicker; import static android.window.OnBackInvokedDispatcher.PRIORITY_DEFAULT; import android.app.FragmentTransaction; import android.content.Intent; import android.os.Bundle; import android.os.LocaleList; import android.provider.Settings; import android.util.Log; import android.view.MenuItem; import android.window.OnBackInvokedCallback; import androidx.core.view.ViewCompat; import com.android.internal.app.LocalePickerWithRegion; import com.android.internal.app.LocaleStore; import com.android.settings.R; import com.android.settings.core.SettingsBaseActivity; /** A activity to show the locale picker page. */ public class LocalePickerWithRegionActivity extends SettingsBaseActivity implements LocalePickerWithRegion.LocaleSelectedListener, MenuItem.OnActionExpandListener { private static final String TAG = LocalePickerWithRegionActivity.class.getSimpleName(); private static final String PARENT_FRAGMENT_NAME = "localeListEditor"; private LocalePickerWithRegion mSelector; private final OnBackInvokedCallback mOnBackInvokedCallback = () -> { handleBackPressed(); }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); getActionBar().setDisplayHomeAsUpEnabled(true); setTitle(R.string.add_a_language); LocaleList explicitLocales = null; if (isDeviceDemoMode()) { Bundle bundle = getIntent().getExtras(); explicitLocales = bundle == null ? null : bundle.getParcelable(Settings.EXTRA_EXPLICIT_LOCALES, LocaleList.class); Log.i(TAG, "Has explicit locales : " + explicitLocales); } getOnBackInvokedDispatcher() .registerOnBackInvokedCallback(PRIORITY_DEFAULT, mOnBackInvokedCallback); mSelector = LocalePickerWithRegion.createLanguagePicker( this, LocalePickerWithRegionActivity.this, false /* translate only */, explicitLocales, null /* appPackageName */, this); getFragmentManager() .beginTransaction() .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN) .replace(R.id.content_frame, mSelector) .addToBackStack(PARENT_FRAGMENT_NAME) .commit(); } @Override public void onDestroy() { super.onDestroy(); getOnBackInvokedDispatcher().unregisterOnBackInvokedCallback(mOnBackInvokedCallback); } @Override public boolean onOptionsItemSelected(MenuItem item) { if (item.getItemId() == android.R.id.home) { handleBackPressed(); return true; } return super.onOptionsItemSelected(item); } @Override public void onLocaleSelected(LocaleStore.LocaleInfo locale) { final Intent intent = new Intent(); intent.putExtra(LocaleListEditor.INTENT_LOCALE_KEY, locale); setResult(RESULT_OK, intent); finish(); } private void handleBackPressed() { if (getFragmentManager().getBackStackEntryCount() > 1) { super.onBackPressed(); } else { setResult(RESULT_CANCELED); finish(); } } private boolean isDeviceDemoMode() { return Settings.Global.getInt( getContentResolver(), Settings.Global.DEVICE_DEMO_MODE, 0) == 1; } @Override public boolean onMenuItemActionExpand(MenuItem item) { // To prevent a large space on tool bar. mAppBarLayout.setExpanded(false /*expanded*/, false /*animate*/); // To prevent user can expand the collpasing tool bar view. ViewCompat.setNestedScrollingEnabled(mSelector.getListView(), false); return true; } @Override public boolean onMenuItemActionCollapse(MenuItem item) { mAppBarLayout.setExpanded(false /*expanded*/, false /*animate*/); ViewCompat.setNestedScrollingEnabled(mSelector.getListView(), true); return true; } } 分析这个类
06-07
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