Exception when calling wait()

Question

I am implementing an application in which I play two sounds ("touchandshow" followed by "tiger"). This is done in my looper method. I call it a first time, then call wait(), then call looper again.

The problem is that I get an exception in the LogCat from the wait() call.

Here is my code:

        mPlayer = MediaPlayer.create(this, R.raw.touchandshow);
    mPlayer2 = MediaPlayer.create(this, R.raw.tiger);

    try {

        looper();
        wait(2000);

        looper();
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

public void looper() {
    CountDownTimer aCounter;
    aCounter = new CountDownTimer(2000, 1000) {
        public void onTick(long millisUntilFinished) {
            mPlayer.start();
        }

        public void onFinish() {
            mPlayer2.start();
        }
    };
    aCounter.start();

}  

And the LogCat:

    07-29 10:20:09.412: ERROR/AndroidRuntime(1188): FATAL EXCEPTION: main
07-29 10:20:09.412: ERROR/AndroidRuntime(1188): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.AudioTesting/com.AudioTesting.AudioTesting}: java.lang.IllegalMonitorStateException: object not locked by thread before wait()
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at android.os.Looper.loop(Looper.java:123)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at android.app.ActivityThread.main(ActivityThread.java:4627)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at java.lang.reflect.Method.invokeNative(Native Method)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at java.lang.reflect.Method.invoke(Method.java:521)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at dalvik.system.NativeStart.main(Native Method)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188): Caused by: java.lang.IllegalMonitorStateException: object not locked by thread before wait()
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at java.lang.Object.wait(Native Method)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at java.lang.Object.wait(Object.java:326)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at com.AudioTesting.AudioTesting.onCreate(AudioTesting.java:25)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
07-29 10:20:09.412: ERROR/AndroidRuntime(1188):     ... 11 more

Can anyone tell me what I'm doing wrong?

Answer 1

java.lang.IllegalMonitorStateException: object not locked by thread before wait()

Your problem is this message. You can't call wait on an object you haven't locked first. wait is meant for synchronization, not as a generic "sleep" facility.

If you just want to pause your thread, use:

Thread.sleep(2000);

inside your try block instead.