我是android新手，正在学习任务。我在使用runnable的教程中找到了这个例子。
public class ThreadExample extends Activity {
Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
TextView myTextView = (TextView)findViewById(R.id.myTextView);
String ReturnedInt = Integer.toString(msg.what);
myTextView.setText(ReturnedInt);
Vibrator v = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
v.vibrate(1500); // Vibrate for 1500 milliseconds
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_thread_example);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.thread_example, menu);
return true;
}
public void buttonClick(View view)
{
Runnable runnable = new Runnable() {
public void run() {
long endTime = System.currentTimeMillis() + 2*1000;
while (System.currentTimeMillis() < endTime) {
synchronized (this) {
try {
wait(endTime - System.currentTimeMillis());
}
catch (Exception e) {
}
}
}
handler.sendEmptyMessage(1234);
}
};
Thread mythread = new Thread(runnable);
mythread.start();
}
}
此代码有效。如果我按下屏幕上的按钮，文本框显示“1234”，振动器振动。我想重新安排一些代码，以实现我编写录音机的最终目标，音频采样将在线程中。我通过将runnable和线程声明移动到类的顶部来重新排列代码，因此我可以从其他方法引用它们
public class ThreadExample extends Activity {
Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
TextView myTextView = (TextView)findViewById(R.id.myTextView);
String ReturnedInt = Integer.toString(msg.what);
myTextView.setText(ReturnedInt);
Vibrator v = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
v.vibrate(1500); // Vibrate for 1500 milliseconds
}
};
Runnable runnable = new Runnable() {
public void run() {
long endTime = System.currentTimeMillis() + 2*1000;
while (System.currentTimeMillis() < endTime) {
synchronized (this) {
try {
wait(endTime - System.currentTimeMillis());
}
catch (Exception e) {
}
}
}
handler.sendEmptyMessage(1234);
}
};
Thread mythread = new Thread(runnable);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_thread_example);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.thread_example, menu);
return true;
}
public void buttonClick(View view)
{
mythread.start();
}
}
如果再次运行应用程序，第一次按下按钮时工作，文本更新，振动器振动，但第二次按下按钮程序崩溃。我认为它可能与被破坏的线程有关，但我认为类的开头的声明在类被销毁之前不会被销毁。它可能是别的东西。
任何想法为什么第二次按下按钮时它会崩溃？
编辑 - 根据要求，这是logcat输出
08-11 09:49:37.489: W/dalvikvm(5014): threadid=1: thread exiting with uncaught exception (group=0x2aac8560)
08-11 09:49:37.509: E/AndroidRuntime(5014): FATAL EXCEPTION: main
08-11 09:49:37.509: E/AndroidRuntime(5014): java.lang.IllegalStateException: Could not execute method of the activity
08-11 09:49:37.509: E/AndroidRuntime(5014): at android.view.View$1.onClick(View.java:2168)
08-11 09:49:37.509: E/AndroidRuntime(5014): at android.view.View.performClick(View.java:2552)
08-11 09:49:37.509: E/AndroidRuntime(5014): at android.view.View$PerformClick.run(View.java:9229)
08-11 09:49:37.509: E/AndroidRuntime(5014): at android.os.Handler.handleCallback(Handler.java:587)
08-11 09:49:37.509: E/AndroidRuntime(5014): at android.os.Handler.dispatchMessage(Handler.java:92)
08-11 09:49:37.509: E/AndroidRuntime(5014): at android.os.Looper.loop(Looper.java:123)
08-11 09:49:37.509: E/AndroidRuntime(5014): at android.app.ActivityThread.main(ActivityThread.java:3701)
08-11 09:49:37.509: E/AndroidRuntime(5014): at java.lang.reflect.Method.invokeNative(Native Method)
08-11 09:49:37.509: E/AndroidRuntime(5014): at java.lang.reflect.Method.invoke(Method.java:507)
08-11 09:49:37.509: E/AndroidRuntime(5014): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
08-11 09:49:37.509: E/AndroidRuntime(5014): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:624)
08-11 09:49:37.509: E/AndroidRuntime(5014): at dalvik.system.NativeStart.main(Native Method)
08-11 09:49:37.509: E/AndroidRuntime(5014): Caused by: java.lang.reflect.InvocationTargetException
08-11 09:49:37.509: E/AndroidRuntime(5014): at java.lang.reflect.Method.invokeNative(Native Method)
08-11 09:49:37.509: E/AndroidRuntime(5014): at java.lang.reflect.Method.invoke(Method.java:507)
08-11 09:49:37.509: E/AndroidRuntime(5014): at android.view.View$1.onClick(View.java:2163)
08-11 09:49:37.509: E/AndroidRuntime(5014): ... 11 more
08-11 09:49:37.509: E/AndroidRuntime(5014): Caused by: java.lang.IllegalThreadStateException: Thread already started.
08-11 09:49:37.509: E/AndroidRuntime(5014): at java.lang.Thread.start(Thread.java:1227)
08-11 09:49:37.509: E/AndroidRuntime(5014): at com.example.threadexample.ThreadExample.buttonClick(ThreadExample.java:60)
08-11 09:49:37.509: E/AndroidRuntime(5014): ... 14 more
答案 0 :(得分：2)
这是主要原因：
Caused by: java.lang.IllegalThreadStateException: Thread already started.
at java.lang.Thread.start(Thread.java:1227)
at com.example.threadexample.ThreadExample.buttonClick(ThreadExample.java:60)
您不能重复使用相同的Thread对象。在再次致电Thread之前，您必须先创建一个新的.start()对象。
不止一次启动线程永远不合法。特别是，a 一旦完成执行，线程可能无法重新启动。