java - 如何通过 tabhost 监听器更改 textview

Question

我是新的android程序员，我不知道如何在OnTabChangeListener调用后设置TextView的新文本。我尝试了很多方法，但每次都显示奇怪的错误。

编辑:(最新代码)

MainActivity.java:

package com.RobsoN;

import android.app.Activity;
import android.app.TabActivity;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.widget.TabHost;
import android.widget.TextView;
import android.widget.TabHost.OnTabChangeListener;
import android.widget.TabHost.TabSpec;

public class MainActivity extends TabActivity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    final TabHost tabHost = getTabHost();

    Log.i("App","App initialization");

    TabSpec start = tabHost.newTabSpec("Start");
    start.setIndicator("Start", getResources().getDrawable(android.R.drawable.ic_menu_rotate));
    Intent photosIntent = new Intent(this, Start.class);
    start.setContent(photosIntent);

    TabSpec settings = tabHost.newTabSpec("Ustawienia");
    settings.setIndicator("Ustawienia", getResources().getDrawable(android.R.drawable.ic_menu_manage));
    Intent songsIntent = new Intent(this, Settings.class);
    settings.setContent(songsIntent);

    TabSpec info = tabHost.newTabSpec("Informacje");
    info.setIndicator("Informacje", getResources().getDrawable(android.R.drawable.ic_menu_help));
    Intent videosIntent = new Intent(this, Other.class);
    info.setContent(videosIntent);

    // Adding all TabSpec to TabHost
    tabHost.addTab(start); 
    tabHost.addTab(settings);
    tabHost.addTab(info); 

    tabHost.setOnTabChangedListener(new OnTabChangeListener(){

        public void onTabChanged(String tabId) {
            if(tabId.equals("Informacje"))
            {
                Other child = (Other) getTabHost().getChildAt(0).getContext(); //Error here: 1 java.lang.ClassCastException: com.RobsoN.MainActivity 2 com.RobsoN.MainActivity$1.onTabChanged(MainActivity.java:50)

                child.refreshInfo();    
            }       
        }});

}

}

其他.java:

package com.RobsoN;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class Other extends Activity {

Button button_update;
TextView stat_lastestappversion;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.tab_other);

    stat_lastestappversion = (TextView) findViewById(R.id.stat_lastestappversion);
    button_update = (Button) findViewById(R.id.button_update);
    button_update.setOnClickListener(new OnClickListener() 
    {
        public void onClick(View v) 
        {

        }
    });
}

public void refreshInfo()
{
    stat_lastestappversion = (TextView) findViewById(R.id.stat_lastestappversion);
    stat_lastestappversion.setText("TEST TEST 321");
}
}

错误:

05-05 13:00:59.845: E/AndroidRuntime(314): FATAL EXCEPTION: main
05-05 13:00:59.845: E/AndroidRuntime(314): java.lang.ClassCastException: com.RobsoN.MainActivity
05-05 13:00:59.845: E/AndroidRuntime(314):  at com.RobsoN.MainActivity$1.onTabChanged(MainActivity.java:50)
05-05 13:00:59.845: E/AndroidRuntime(314):  at android.widget.TabHost.invokeOnTabChangeListener(TabHost.java:356)
05-05 13:00:59.845: E/AndroidRuntime(314):  at android.widget.TabHost.setCurrentTab(TabHost.java:341)
05-05 13:00:59.845: E/AndroidRuntime(314):  at android.widget.TabHost$2.onTabSelectionChanged(TabHost.java:129)
05-05 13:00:59.845: E/AndroidRuntime(314):  at android.widget.TabWidget$TabClickListener.onClick(TabWidget.java:453)
05-05 13:00:59.845: E/AndroidRuntime(314):  at android.view.View.performClick(View.java:2408)
05-05 13:00:59.845: E/AndroidRuntime(314):  at android.view.View$PerformClick.run(View.java:8816)
05-05 13:00:59.845: E/AndroidRuntime(314):  at android.os.Handler.handleCallback(Handler.java:587)
05-05 13:00:59.845: E/AndroidRuntime(314):  at android.os.Handler.dispatchMessage(Handler.java:92)
05-05 13:00:59.845: E/AndroidRuntime(314):  at android.os.Looper.loop(Looper.java:123)
05-05 13:00:59.845: E/AndroidRuntime(314):  at android.app.ActivityThread.main(ActivityThread.java:4627)
05-05 13:00:59.845: E/AndroidRuntime(314):  at java.lang.reflect.Method.invokeNative(Native Method)
05-05 13:00:59.845: E/AndroidRuntime(314):  at java.lang.reflect.Method.invoke(Method.java:521)
05-05 13:00:59.845: E/AndroidRuntime(314):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
05-05 13:00:59.845: E/AndroidRuntime(314):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
05-05 13:00:59.845: E/AndroidRuntime(314):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

正如 Luksprog 所说，您不能像在 java 中那样使用 Activity 的直接初始化。据我所知，您想在选项卡主机的子 Activity 中显示 TextView 。为此，您可以使用以下内容

  Other child = (Other) getTabHost().getChildAt(0).getContext();
  child.refreshInfo();

注意

由于您是新的 Android 程序员，强烈建议从 Fragments 开始。选项卡概念很久以前就已被弃用。老程序员可能仍然会使用它来支持他们现有的程序，但作为新程序员，你最好避免它。

更新:

你可以做另一件事

getTabHost().setCurrentTab(tabindex);
Other child= (Other) this.getCurrentActivity();
child.refreshInfo();