为什么On Click Listener崩溃了我的Android应用程序？

Question

So, as a bit of background, I am currently an iOS developer, and I wanted to branch out and develop for android as well, and I finally found time to do so. 因此，作为背景，我目前是一名iOS开发人员，我也想分支并为android开发，我终于找到了时间。

I've been watching some video tutorials on developing for android, and in the lesson we made a simple app that when you click one button it adds 1 and when you click another it subtracts. 我一直在观看一些针对Android开发的视频教程，在本课中，我们制作了一个简单的应用程序，当您单击一个按钮时，它加1，而当您单击另一个按钮时，它减一。

There's also a small textview which the number value of the total changes as well when the button is clicked, all of which can be easily identified in the code. 还有一个小的textview，单击按钮时，总数的数值也会发生变化，所有这些都可以在代码中轻松识别。

However, when I build and run the app, it displays an error on the screen saying "Unfortunately (Name of app) has stopped." 但是，当我构建并运行该应用程序时，它在屏幕上显示错误，提示“不幸的是（应用程序名称）已停止。”

Add upon debugging the app only stops working and displays this message after I add my first On Click Listener method. 添加调试后，应用程序只会停止运行，并在添加第一个On Click Listener方法后显示此消息。

Here is the main XML: 这是主要的XML：

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Your total is 0" 
        android:textSize="45dp"
        android:layout_gravity="center"
        android:gravity="center"
        android:id="@+id/tvDisplay"
/>
    <Button 
    android:layout_width="250dp"
    android:layout_height="wrap_content"
    android:text="Add One"
    android:layout_gravity="center"
    android:textSize="20dp"
    android:id="@+id/bAdd"
/>     

    <Button 
    android:layout_width="250dp"
    android:layout_height="wrap_content"
    android:text="Subtract One"
    android:layout_gravity="center"
    android:textSize="20dp"
    android:id="@+id/bSub"
/>   


</LinearLayout>

Here is the Manifest XML: 这是清单XML：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.tutorial.thenewboston"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="13"
        android:targetSdkVersion="19" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.tutorial.thenewboston.StartingPoint"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Here is the Java: 这是Java：

public class StartingPoint extends ActionBarActivity {

int counter;
Button add, sub;
TextView display;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_starting_point);
    counter = 0;
    add = (Button) findViewById(R.id.bAdd);
    sub = (Button) findViewById(R.id.bSub);
    display = (TextView) findViewById(R.id.tvDisplay);
    add.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            counter++;
            display.setText("Your total is " + counter);


        }
    });
    sub.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            counter--;
            display.setText("Your total is " + counter);


        }
    });

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
    }
}

Here is the LogCat: 这是LogCat：

03-14 14:53:41.111: D/AndroidRuntime(17884): Shutting down VM
03-14 14:53:41.111: W/dalvikvm(17884): threadid=1: thread exiting with uncaught exception (group=0x41ce4ba8)
03-14 14:53:41.111: E/AndroidRuntime(17884): FATAL EXCEPTION: main
03-14 14:53:41.111: E/AndroidRuntime(17884): Process: com.tutorial.thenewboston, PID: 17884
03-14 14:53:41.111: E/AndroidRuntime(17884): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tutorial.thenewboston/com.tutorial.thenewboston.StartingPoint}: java.lang.NullPointerException
03-14 14:53:41.111: E/AndroidRuntime(17884):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at android.os.Handler.dispatchMessage(Handler.java:102)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at android.os.Looper.loop(Looper.java:136)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at android.app.ActivityThread.main(ActivityThread.java:5017)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at java.lang.reflect.Method.invokeNative(Native Method)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at java.lang.reflect.Method.invoke(Method.java:515)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at dalvik.system.NativeStart.main(Native Method)
03-14 14:53:41.111: E/AndroidRuntime(17884): Caused by: java.lang.NullPointerException
03-14 14:53:41.111: E/AndroidRuntime(17884):    at com.tutorial.thenewboston.StartingPoint.onCreate(StartingPoint.java:31)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at android.app.Activity.performCreate(Activity.java:5231)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-14 14:53:41.111: E/AndroidRuntime(17884):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
03-14 14:53:41.111: E/AndroidRuntime(17884):    ... 11 more

Console Log: 控制台日志：

[2014-03-14 15:09:31 - TheNewBoston] ------------------------------
[2014-03-14 15:09:31 - TheNewBoston] Android Launch!
[2014-03-14 15:09:31 - TheNewBoston] adb is running normally.
[2014-03-14 15:09:31 - TheNewBoston] Performing com.tutorial.thenewboston.StartingPoint activity launch
[2014-03-14 15:09:31 - TheNewBoston] Automatic Target Mode: using device '015d483bce140216'
[2014-03-14 15:09:31 - TheNewBoston] Application already deployed. No need to reinstall.
[2014-03-14 15:09:31 - TheNewBoston] Starting activity com.tutorial.thenewboston.StartingPoint on device 015d483bce140216
[2014-03-14 15:09:32 - TheNewBoston] ActivityManager: Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=com.tutorial.thenewboston/.StartingPoint }

And here is some more hopefully relevant information: I'm testing my apps on my personal Android Tablet not the Simulator, because the sim is dirt slow. 以下是一些与希望相关的信息：我在我的个人Android平板电脑上而不是在模拟器上测试我的应用程序，因为模拟程序运行缓慢。 My tablet is an Asus Nexus 7, with NVIDIA Tegra 3 1.20GHz 1GB RAM, 32GB Flash Storage and is running Kit Kat, 4.4.2 我的平板电脑是Asus Nexus 7，具有NVIDIA Tegra 3 1.20GHz 1GB RAM，32GB闪存，并运行Kit Kat，4.4.2。

EDIT: 编辑：

My previous java contained an error which was linking it to my main XML view. 我以前的Java包含一个错误，该错误将其链接到我的主要XML视图。 it was calling activity_starting_point when it should have been calling fragment_starting_point. 它本应调用fragment_starting_point时正在调用activity_starting_point。

This is the new code 这是新代码

public class StartingPoint extends ActionBarActivity {

    int counter;
    Button add, sub;
    TextView display;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_starting_point);
        add = (Button) findViewById(R.id.bAdd);
        sub = (Button) findViewById(R.id.bSub);
        display = (TextView) findViewById(R.id.tvDisplay);
        add.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                counter++;
                display.setText("Your total is " + counter);


            }
        });
        sub.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                counter--;
                display.setText("Your total is " + counter);


            }
        });

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
    }

However my problem is the exact same, the app crashes with the same message as before, but it does contain new logcat info: 但是我的问题是完全一样的，该应用程序崩溃并显示与以前相同的消息，但是它确实包含新的logcat信息：

03-14 15:25:44.621: E/FragmentManager(20269): No view found for id 0x7f05003c (com.tutorial.thenewboston:id/container) for fragment PlaceholderFragment{4247a988 #0 id=0x7f05003c}
03-14 15:25:44.621: E/FragmentManager(20269): Activity state:
03-14 15:25:44.621: D/FragmentManager(20269):   Local FragmentActivity 4245cf60 State:
03-14 15:25:44.621: D/FragmentManager(20269):     mCreated=truemResumed=false mStopped=false mReallyStopped=false
03-14 15:25:44.621: D/FragmentManager(20269):     mLoadersStarted=false
03-14 15:25:44.621: D/FragmentManager(20269):   Active Fragments in 4245e0b8:
03-14 15:25:44.621: D/FragmentManager(20269):     #0: PlaceholderFragment{4247a988 #0 id=0x7f05003c}
03-14 15:25:44.621: D/FragmentManager(20269):       mFragmentId=#7f05003c mContainerId=#7f05003c mTag=null
03-14 15:25:44.621: D/FragmentManager(20269):       mState=0 mIndex=0 mWho=android:fragment:0 mBackStackNesting=0
03-14 15:25:44.621: D/FragmentManager(20269):       mAdded=true mRemoving=false mResumed=false mFromLayout=false mInLayout=false
03-14 15:25:44.621: D/FragmentManager(20269):       mHidden=false mDetached=false mMenuVisible=true mHasMenu=false
03-14 15:25:44.621: D/FragmentManager(20269):       mRetainInstance=false mRetaining=false mUserVisibleHint=true
03-14 15:25:44.621: D/FragmentManager(20269):       mFragmentManager=FragmentManager{4245e0b8 in StartingPoint{4245cf60}}
03-14 15:25:44.621: D/FragmentManager(20269):       mActivity=com.tutorial.thenewboston.StartingPoint@4245cf60
03-14 15:25:44.621: D/FragmentManager(20269):   Added Fragments:
03-14 15:25:44.621: D/FragmentManager(20269):     #0: PlaceholderFragment{4247a988 #0 id=0x7f05003c}
03-14 15:25:44.621: D/FragmentManager(20269):   FragmentManager misc state:
03-14 15:25:44.621: D/FragmentManager(20269):     mActivity=com.tutorial.thenewboston.StartingPoint@4245cf60
03-14 15:25:44.621: D/FragmentManager(20269):     mContainer=android.support.v4.app.FragmentActivity$2@4245ea30
03-14 15:25:44.621: D/FragmentManager(20269):     mCurState=2 mStateSaved=false mDestroyed=false
03-14 15:25:44.621: D/FragmentManager(20269):   View Hierarchy:
03-14 15:25:44.621: D/FragmentManager(20269):     com.android.internal.policy.impl.PhoneWindow$DecorView{424636b0 V.E..... ... 0,0-0,0}
03-14 15:25:44.621: D/FragmentManager(20269):       com.android.internal.widget.ActionBarOverlayLayout{424646a0 V.ED.... ... 0,0-0,0 #1020313 android:id/action_bar_overlay_layout}
03-14 15:25:44.621: D/FragmentManager(20269):         android.widget.FrameLayout{42465448 V.E..... ... 0,0-0,0 #1020002 android:id/content}
03-14 15:25:44.631: D/FragmentManager(20269):           android.widget.LinearLayout{42472528 V.E..... ... 0,0-0,0}
03-14 15:25:44.631: D/FragmentManager(20269):             android.widget.TextView{42472840 V.ED.... ... 0,0-0,0 #7f05003d app:id/tvDisplay}
03-14 15:25:44.631: D/FragmentManager(20269):             android.widget.Button{42472e30 VFED..C. ... 0,0-0,0 #7f05003e app:id/bAdd}
03-14 15:25:44.631: D/FragmentManager(20269):             android.widget.Button{42473838 VFED..C. ... 0,0-0,0 #7f05003f app:id/bSub}
03-14 15:25:44.631: D/FragmentManager(20269):         com.android.internal.widget.ActionBarContainer{42465960 V.ED.... ... 0,0-0,0 #1020314 android:id/action_bar_container}
03-14 15:25:44.631: D/FragmentManager(20269):           com.android.internal.widget.ActionBarView{42465fb8 V.E..... ... 0,0-0,0 #1020315 android:id/action_bar}
03-14 15:25:44.631: D/FragmentManager(20269):             android.widget.LinearLayout{42466718 V.....C. ... 0,0-0,0}
03-14 15:25:44.631: D/FragmentManager(20269):               com.android.internal.widget.ActionBarView$HomeView{42467a90 V.E..... ... 0,0-0,0}
03-14 15:25:44.631: D/FragmentManager(20269):                 android.widget.ImageView{42467f58 G.ED.... ... 0,0-0,0 #102025a android:id/up}
03-14 15:25:44.631: D/FragmentManager(20269):                 android.widget.ImageView{42469038 V.ED.... ... 0,0-0,0 #102002c android:id/home}
03-14 15:25:44.631: D/FragmentManager(20269):               android.widget.LinearLayout{4246a3f0 G.E..... ... 0,0-0,0}
03-14 15:25:44.631: D/FragmentManager(20269):                 android.widget.TextView{4246a890 V.ED.... ... 0,0-0,0 #1020265 android:id/action_bar_title}
03-14 15:25:44.631: D/FragmentManager(20269):                 android.widget.TextView{4246b578 G.ED.... ... 0,0-0,0 #1020266 android:id/action_bar_subtitle}
03-14 15:25:44.631: D/FragmentManager(20269):           com.android.internal.widget.ActionBarContextView{4246bc60 G.E..... ... 0,0-0,0 #1020316 android:id/action_context_bar}
03-14 15:25:44.631: D/FragmentManager(20269):         com.android.internal.widget.ActionBarContainer{4246c248 G.ED.... ... 0,0-0,0 #1020317 android:id/split_action_bar}
03-14 15:25:44.631: D/AndroidRuntime(20269): Shutting down VM
03-14 15:25:44.631: W/dalvikvm(20269): threadid=1: thread exiting with uncaught exception (group=0x41ce4ba8)
03-14 15:25:44.631: E/AndroidRuntime(20269): FATAL EXCEPTION: main
03-14 15:25:44.631: E/AndroidRuntime(20269): Process: com.tutorial.thenewboston, PID: 20269
03-14 15:25:44.631: E/AndroidRuntime(20269): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tutorial.thenewboston/com.tutorial.thenewboston.StartingPoint}: java.lang.IllegalArgumentException: No view found for id 0x7f05003c (com.tutorial.thenewboston:id/container) for fragment PlaceholderFragment{4247a988 #0 id=0x7f05003c}
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.os.Handler.dispatchMessage(Handler.java:102)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.os.Looper.loop(Looper.java:136)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.app.ActivityThread.main(ActivityThread.java:5017)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at java.lang.reflect.Method.invokeNative(Native Method)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at java.lang.reflect.Method.invoke(Method.java:515)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at dalvik.system.NativeStart.main(Native Method)
03-14 15:25:44.631: E/AndroidRuntime(20269): Caused by: java.lang.IllegalArgumentException: No view found for id 0x7f05003c (com.tutorial.thenewboston:id/container) for fragment PlaceholderFragment{4247a988 #0 id=0x7f05003c}
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:919)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:570)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.app.Activity.performStart(Activity.java:5241)
03-14 15:25:44.631: E/AndroidRuntime(20269):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2168)
03-14 15:25:44.631: E/AndroidRuntime(20269):    ... 11 more

Answer 1

EDIT: 编辑：

I just watched the tutoiral: 我只是看了tutoiral：

You are setting the wrong layout file: 您设置了错误的布局文件：

setContentView(R.layout.activity_starting_point);

You are supposed to set: 您应该设置：

setContentView(R.layout.main);

Assuming what you are saying in your question is correct and the XML code you posted really belongs to "main.xml". 假设您在问题中所说的是正确的，并且您发布的XML代码确实属于“ main.xml”。 This is why you are getting a NullPointerException . 这就是为什么您得到NullPointerException 。 The Views (TextView, Button, ...) you are trying to reference are not in the layout file you set as the content view. 您尝试引用的视图（TextView，Button等）不在您设置为内容视图的布局文件中 。

Answer 2

Try this: 尝试这个：

add = (Button) findViewById(R.id.bAdd);
        sub = (Button) findViewById(R.id.bSub);
        display = (TextView) findViewById(R.id.tvDisplay);
        add.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                counter++;
                display.setText("Your total is " + counter);


            }
        });
        sub.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                counter--;
                display.setText("Your total is " + counter);


            }
        });

Regards. 问候。 Jose 何塞

为什么On Click Listener崩溃了我的Android应用程序？

问题描述

2 个解决方案

解决方案1
4 已采纳 2014-03-14 19:08:32

解决方案2
0 2014-03-14 19:49:25

为什么On Click Listener崩溃了我的Android应用程序？

问题描述

2 个解决方案

解决方案1 4 已采纳 2014-03-14 19:08:32

解决方案2 0 2014-03-14 19:49:25

解决方案1
4 已采纳 2014-03-14 19:08:32

解决方案2
0 2014-03-14 19:49:25