Android 从父 Activity 访问 TabHost 视图

Question

我有一个 tabhost 视图，里面有一个 FrameLayout，一旦在我的 java 中选择了一个选项卡，我就会创建新的意图并在 FrameLayout 中调用不同的活动。

现在我正在尝试从父活动访问子活动（FrameLayout 内的那个）视图，但它不起作用。下面是示例代码

    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.book_download_activity);

        tabHost = getTabHost();
        addTab("Download File", R.drawable.ic_action_download,DownloadActivity.class);

   }

    private void addTab(String labelId, int drawable, Class<?> c) {
    Intent intent = new Intent(this, c);
    TabHost.TabSpec spec = tabHost.newTabSpec(labelId);

    View tabIndicator = LayoutInflater.from(this).inflate(R.layout.custom_tabs, getTabWidget(), false);
    TextView title = (TextView) tabIndicator.findViewById(R.id.title);
    title.setText(labelId);

    ImageView icon = (ImageView) tabIndicator.findViewById(R.id.icon);
    icon.setImageResource(drawable);
    icon.setScaleType(ImageView.ScaleType.FIT_CENTER);

    spec.setIndicator(tabIndicator);
    spec.setContent(intent);
    tabHost.addTab(spec);
}

现在名为 DownloadActivity 的活动有它自己的 xml 布局，我想从这个活动中访问它

错误日志

                02-15 06:08:09.147: E/AndroidRuntime(2588): FATAL EXCEPTION: main
            02-15 06:08:09.147: E/AndroidRuntime(2588): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.utext.unext/com.utext.unext.BookFrame}: java.lang.NullPointerException
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at android.os.Handler.dispatchMessage(Handler.java:99)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at android.os.Looper.loop(Looper.java:137)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at android.app.ActivityThread.main(ActivityThread.java:5039)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at java.lang.reflect.Method.invokeNative(Native Method)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at java.lang.reflect.Method.invoke(Method.java:511)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at dalvik.system.NativeStart.main(Native Method)
            02-15 06:08:09.147: E/AndroidRuntime(2588): Caused by: java.lang.NullPointerException
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at com.utext.unext.BookFrame.createView(BookFrame.java:190)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at com.utext.unext.BookFrame.onCreate(BookFrame.java:62)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at android.app.Activity.performCreate(Activity.java:5104)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
            02-15 06:08:09.147: E/AndroidRuntime(2588):     ... 11 more

希望有意义

Answer 1

我有类似的问题。这是我的代码

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Removes the title bar
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);
    Intent i = getIntent();
    mExtras = i.getExtras();
    mScreenNum = mExtras.getString("num");
    setContentView(R.layout.tab);
    int a = Integer.parseInt(mScreenNum);
                     this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
    title = (TextView) findViewById(R.id.title_money2);
    // Removes the default keyboard
    this.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_PAN);
    TabHost tabHost = getTabHost();
    // Creating tab here
    ImageView iv_tabl_selected = new ImageView(this);
    iv_tabl_selected.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, 1f));
    iv_tabl_selected.setImageResource(R.drawable.tab_indicator_bill);

    ImageView iv_tab2_selected = new ImageView(this);
    iv_tab2_selected.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, 1f));
    iv_tab2_selected.setImageResource(R.drawable.tab_indicator_recharge);

    ImageView iv_tab3_selected = new ImageView(this);
    iv_tab3_selected.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, 1f));
    iv_tab3_selected.setImageResource(R.drawable.tab_indicator_dth);

    // Displaying the Tab host which are created
    TabSpec tab_first= tabHost.newTabSpec("One");
    tab_first.setIndicator(iv_tabl_selected);
    TabSpec tab_second= tabHost.newTabSpec("two");
    tab_second.setIndicator(iv_tab2_selected);
    TabSpec tab_three = tabHost.newTabSpec("three");
    tab_three.setIndicator(iv_tab3_selected);

    // Switching between Tabs
    mActivity1 = new Intent(this, Activity1.class);
    mActivity2= new Intent(this, Activity2.class);
    mActivity3= new Intent(this, Activity3.class);
    tab_first.setContent(mActivity1 );
    tab_second.setContent(mActivity2);
    tab_three.setContent(mActivity3);

    // The order in which the tabs are displayed
    tabHost.addTab(tab_first);
    tabHost.addTab(tab_second);
    tabHost.addTab(ttab_three);
    //tabHost.getTabWidget().getChildTabViewAt(2).setOnClickListener(null);

    // Switch case to select Tab from Home screen
    switch (a) {
    case TAB1:
        tabHost.setCurrentTab(0);
        tab_recharge.setIndicator(iv_tabl_selected);
        break;

    case TAB2:
        tabHost.setCurrentTab(1);
        tab_dth.setIndicator(iv_tab2_selected);
        break;

    case TAB3:
        tabHost.setCurrentTab(2);
        tab_billpayment.setIndicator(iv_tab3_selected);
        break;
    }


        }
    });

}

}