方法出错，只有在添加其他不相关的代码之后

时间：2014-05-03 06:37:04

标签： android android-studio fragment-tab-host

不确定该怎么想这个问题。我为我的标签设置创建的这个方法名为tabSetUp()，我之前创建过，并使用我的onCreate方法调用，从那时起它已成功运行。现在，我突然在我的主要活动的另一个区域添加代码，现在我收到应用程序崩溃，说这是由我的选项卡设置方法引起的。没有意义。我错过了什么吗？我添加的新代码没有错误，但确实有黄色警告，说可能有空指针异常（我不太了解）。为什么我的应用程序崩溃了？谢谢你的帮助。 LogCat在下面。

MainSelectorActivity.java 

package com.azurespot.disastertimer.app;

import android.content.Intent;
import android.content.SharedPreferences;
import android.content.res.Resources;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTabHost;
import android.view.View;
import android.widget.Button;
import android.widget.TabWidget;

import com.azurespot.disastertimer.app.tabs.GodzillaTab;
import com.azurespot.disastertimer.app.tabs.NuclearTab;
import com.azurespot.disastertimer.app.tabs.TsunamiTab;
import com.azurespot.disastertimer.app.tabs.VolcanoTab;
import com.azurespot.disastertimer.app.tabs.ZombieTab;
import com.azurespot.disastertimer.app.themedactivities.GodzillaThemedActivity;
import com.azurespot.disastertimer.app.themedactivities.NuclearThemedActivity;
import com.azurespot.disastertimer.app.themedactivities.TsunamiThemedActivity;
import com.azurespot.disastertimer.app.themedactivities.VolcanoThemedActivity;
import com.azurespot.disastertimer.app.themedactivities.ZombieThemedActivity;


public class MainSelectorActivity extends FragmentActivity {

    Resources resrc;
    FragmentTabHost tabHost;
    private Button btnStart;
    public static final String TABTIMER = "Tab_and_Timer";
    private String selectedTab;

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

        tabSetUp();

        btnStart = (Button) findViewById(R.id.btnStart);
        btnStart.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                goToThemedActivity();
            }
        });

        tabListener();
        changeTabIndicators();
        tabAndTimerPersist();

    }

    public void tabSetUp() {
        resrc = getResources();

        // TabHost setup & functionality
        tabHost = (android.support.v4.app.FragmentTabHost)findViewById(android.R.id.tabhost);
        tabHost.setup(this, getSupportFragmentManager(), R.id.realtabcontent);

        //------Zombie tab------
        //Creates tab and sets zombie icon in tab
        tabHost.addTab(tabHost.newTabSpec("zombie").setIndicator("",
                        getResources().getDrawable(R.drawable.ic_tab_zombie_selected)),
                ZombieTab.class, null);

        //------Nuclear tab------
        //Creates tab and sets nuclear icon in tab
        tabHost.addTab(tabHost.newTabSpec("nuclear").setIndicator("",
                        getResources().getDrawable(R.drawable.ic_tab_nuclear_selected)),
                NuclearTab.class, null);

        //------Tsunami tab------
        //Creates tab and sets tsunami icon in tab
        tabHost.addTab(tabHost.newTabSpec("tsunami").setIndicator("",
                        getResources().getDrawable(R.drawable.ic_tab_tsunami_selected)),
                TsunamiTab.class, null);

        //------Godzilla tab------
        //Creates tab and sets tsunami icon in tab
        tabHost.addTab(tabHost.newTabSpec("godzilla").setIndicator("",
                        getResources().getDrawable(R.drawable.ic_tab_godzilla_selected)),
                GodzillaTab.class, null);

        //------Volcano tab------
        //Creates tab and sets volcano icon in tab
        tabHost.addTab(tabHost.newTabSpec("volcano").setIndicator("",
                        getResources().getDrawable(R.drawable.ic_tab_volcano_selected)),
                VolcanoTab.class, null);

        //set Zombie tab as default (zero based)
        tabHost.setCurrentTab(0);
    }

    // Sets up the tabs to return a value, based on which one is currently selected.
    // The int values will be used in the Start button's onClick to go to the corresponding activity.
    public void tabListener() {
        tabHost.setOnTabChangedListener(new FragmentTabHost.OnTabChangeListener() {
            @Override
            public void onTabChanged(String tabId) {
                selectedTab = tabId;
            }
        });
    }

    public void changeTabIndicators() {
        tabHost = (android.support.v4.app.FragmentTabHost)findViewById(R.id.tabhost);
        TabWidget widget = tabHost.getTabWidget();
        for(int i = 0; i < widget.getTabCount(); i++) {
            View v = widget.getChildTabViewAt(i);

//            // Look for the title view to ensure this is an indicator and not a divider.
//            TextView tv = (TextView)v.findViewById(android.R.id.title);
//            if(tv == null) {
//                continue;
//            }
            v.setBackgroundResource(R.drawable.tab_selector_color);
        }
    }

    public void goToThemedActivity() {

        if (selectedTab.equals("zombie")) {
            Intent i = new Intent(MainSelectorActivity.this, ZombieThemedActivity.class);
            startActivity(i);
        } else if (selectedTab.equals("nuclear")) {
            Intent j = new Intent(MainSelectorActivity.this, NuclearThemedActivity.class);
            startActivity(j);
        } else if (selectedTab.equals("tsunami")) {
            Intent k = new Intent(MainSelectorActivity.this, TsunamiThemedActivity.class);
            startActivity(k);
        } else if (selectedTab.equals("godzilla")) {
            Intent l = new Intent(MainSelectorActivity.this, GodzillaThemedActivity.class);
            startActivity(l);
        } else if (selectedTab.equals("volcano")) {
            Intent m = new Intent(MainSelectorActivity.this, VolcanoThemedActivity.class);
            startActivity(m);
        }
    }

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

    private void tabAndTimerPersist() {

        SharedPreferences prefs = getSharedPreferences(TABTIMER, MODE_PRIVATE);

        SharedPreferences.Editor editor = prefs.edit();
        editor.putInt("zombie", 0);
        editor.putInt("nuclear", 0);
        editor.putInt("tsunami", 0);
        editor.putInt("godzilla", 0);
        editor.putInt("volcano", 0);
        editor.commit();
    }
}

logcat的 

  1054-1054/com.azurespot.disastertimer.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.azurespot.disastertimer.app/com.azurespot.disastertimer.app.MainSelectorActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
            at android.app.ActivityThread.access$600(ActivityThread.java:130)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4745)
            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:786)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.azurespot.disastertimer.app.MainSelectorActivity.tabSetUp(MainSelectorActivity.java:60)
            at com.azurespot.disastertimer.app.MainSelectorActivity.onCreate(MainSelectorActivity.java:38)
            at android.app.Activity.performCreate(Activity.java:5008)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
            at android.app.ActivityThread.access$600(ActivityThread.java:130)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4745)
            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:786)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
            at dalvik.system.NativeStart.main(Native Method)

activity_main_selector.xml 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#7d8794"
    tools:context="com.azurespot.disastertimer.app.MainSelectorActivity">

    <android.support.v4.app.FragmentTabHost
        android:id="@+id/tabhost"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <LinearLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="match_parent" >

            <TabWidget
                android:id="@android:id/tabs"
                android:orientation="horizontal"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="0" />

            <FrameLayout
                android:id="@android:id/tabcontent"
                android:layout_width="0dp"
                android:layout_height="0dp"
                android:layout_weight="0"
                android:measureAllChildren="true"/>

            <FrameLayout
                android:id="@+id/realtabcontent"
                android:layout_width="match_parent"
                android:layout_height="0dp"
                android:layout_weight="1" />

        </LinearLayout>
    </android.support.v4.app.FragmentTabHost>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:orientation="horizontal"
        android:layout_marginTop="180dp"
        android:gravity="center_horizontal">

        <NumberPicker
            android:id="@+id/numberPicker1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="16dp"
            android:layout_marginTop="0dp" />

        <NumberPicker
            android:id="@+id/numberPicker2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="14dp"
            android:layout_marginTop="0dp" />

        <NumberPicker
            android:id="@+id/numberPicker3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="14dp"
            android:layout_marginTop="0dp" />

    </LinearLayout>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="80dp"
        android:layout_alignParentBottom="true"
        android:gravity="center" >

    <Button
        android:id="@+id/btnStart"
        android:layout_gravity="center"
        android:layout_marginBottom="20dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#ed872d"
        android:text="@string/btn_start"
        android:onClick="saveAndStartTimer"/>

    </RelativeLayout>

</RelativeLayout>

1 个答案:

答案 0 :(得分：1)

从

更改此内容 
 tabHost = (android.support.v4.app.FragmentTabHost)findViewById(android.R.id.tabhost);

到

 tabHost = (FragmentTabHost)findViewById(R.id.tabhost);
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