我是 Android 新手，我正在尝试完成一个关于将 aProgressBar与Handler. 请注意，我的目标是 API 11。
这是我的代码，其中包含我正在内联的错误：
public class HandlerDemo extends Activity {
ProgressBar bar;
Handler handler = new Handler() {
@Override
public void handleMessage() { // Shows "method must override or implement supertype method" on this line.
bar.incrementProgressBy(5);
}
@Override
public void close() {
}
@Override
public void flush() {
}
@Override
public void publish(LogRecord arg0) {
}
};
AtomicBoolean isRunning = new AtomicBoolean(false);
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_handler_demo);
bar = (ProgressBar)findViewById(android.R.id.progress);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_handler_demo, menu);
return true;
}
public void onStart() {
super.onStart();
bar.setProgress(0);
Thread background = new Thread(new Runnable() {
@Override
public void run() {
try {
for(int i = 0; i < 20 && isRunning.get(); i++) {
Thread.sleep(1000);
handler.sendMessage(handler.obtainMessage()); // Shows "Method is undefined for type Handler" on this line.
}
} catch(Throwable t) { }
}
});
isRunning.set(true);
background.start();
}
public void onStop() {
super.onStop();
isRunning.set(false);
}
}
为什么我会收到这些错误？