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社区首页 >问答首页 >NullPointerException on CountDownTimer

问NullPointerException on CountDownTimer
EN

Stack Overflow用户
提问于 2014-08-10 11:13:13
回答 1查看 163关注 0票数 0

在我的CuntdownTimerProject中，我对NullPointerException有一个问题。我找不到代码中的错误。我还查看了关于NullPointerException的不同线程，但它们根本帮不了我。

这是我的onCreate：

代码语言：javascript
复制
 public void onCreate(Bundle savedInstanceState) {


        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        btnStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startWorkoutTimer(0);

            }
        });
        btnStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (workoutTimer!=null ){
                    workoutTimer.cancel();

                }
                if (restTimer!=null ){
                    restTimer.cancel();
                }
            }
        });

    }

我这里只用了"null“。logcat还告诉我，NullPointerExeption问题来自于onCreate方法。

逻辑猫：

代码语言：javascript
复制
08-10 13:01:58.254  20626-20626/com.stacktesttimer.app D/dalvikvm﹕ Late-enabling CheckJNI
08-10 13:01:58.314  20626-20626/com.stacktesttimer.app D/AndroidRuntime﹕ Shutting down VM
08-10 13:01:58.314  20626-20626/com.stacktesttimer.app W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41628ba8)
08-10 13:01:58.324  20626-20626/com.stacktesttimer.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.stacktesttimer.app, PID: 20626
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.stacktesttimer.app/com.stacktesttimer.app.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.stacktesttimer.app.MainActivity.onCreate(MainActivity.java:24)
            at android.app.Activity.performCreate(Activity.java:5231)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)
08-10 13:02:30.834  20626-20626/com.stacktesttimer.app I/Process﹕ Sending signal. PID: 20626 SIG: 9
08-10 13:03:10.524  20845-20845/com.stacktesttimer.app D/dalvikvm﹕ Late-enabling CheckJNI
08-10 13:03:10.604  20845-20845/com.stacktesttimer.app D/AndroidRuntime﹕ Shutting down VM
08-10 13:03:10.604  20845-20845/com.stacktesttimer.app W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41628ba8)
08-10 13:03:10.604  20845-20845/com.stacktesttimer.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.stacktesttimer.app, PID: 20845
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.stacktesttimer.app/com.stacktesttimer.app.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.stacktesttimer.app.MainActivity.onCreate(MainActivity.java:24)
            at android.app.Activity.performCreate(Activity.java:5231)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)
08-10 13:04:06.714  20845-20845/com.stacktesttimer.app I/Process﹕ Sending signal. PID: 20845 SIG: 9
08-10 13:11:31.134  21456-21456/com.stacktesttimer.app D/dalvikvm﹕ Late-enabling CheckJNI
08-10 13:11:31.154  21456-21462/com.stacktesttimer.app D/dalvikvm﹕ Debugger has detached; object registry had 1 entries
08-10 13:11:31.224  21456-21456/com.stacktesttimer.app D/AndroidRuntime﹕ Shutting down VM
08-10 13:11:31.224  21456-21456/com.stacktesttimer.app W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41628ba8)
08-10 13:11:31.224  21456-21456/com.stacktesttimer.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.stacktesttimer.app, PID: 21456
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.stacktesttimer.app/com.stacktesttimer.app.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.stacktesttimer.app.MainActivity.onCreate(MainActivity.java:24)
            at android.app.Activity.performCreate(Activity.java:5231)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)

谢谢已经提前了。

完整代码：

代码语言：javascript
复制
public class MainActivity extends Activity {


    CountDownTimer workoutTimer;
    CountDownTimer restTimer;
    Button btnStart, btnStop;

    @Override
    public void onCreate(Bundle savedInstanceState) {


        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        btnStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startWorkoutTimer(0);

            }
        });
        btnStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (workoutTimer!=null ){
                    workoutTimer.cancel();

                }
                if (restTimer!=null ){
                    restTimer.cancel();
                }
            }
        });

    }


    public void startWorkoutTimer(final int count ){


        workoutTimer=new CountDownTimer(30000, 1000) {
            @Override
            public void onTick(long millisUntilFinished) {

            }

            @Override
            public void onFinish() {

                if(count!=3){
                    startRestTimer(count);
                }

            }
        };
        workoutTimer.start();

    }


    public void startRestTimer(final int count ){


        restTimer=new CountDownTimer(15000, 1000) {
            @Override
            public void onTick(long millisUntilFinished) {

            }

            @Override
            public void onFinish() {

                if(count!=3){
                    startWorkoutTimer(count+1);
                }

            }
        };
        restTimer.start();

    }
java
android
nullpointerexception
EN

回答 1

Stack Overflow用户

回答已采纳

发布于 2014-08-10 11:27:12

btnStop和btnStart不是无效的

你得让他们

代码语言：javascript
复制
btnStart = findViewById(R.id.yourStartbuttonId);
票数 2
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/25228008

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