java - Android 按钮在启动线程后不显示

Question

嘿，

我是 Android 开发新手，正在阅读书籍来熟悉它。这段代码在一本书上也有，但到目前为止还不起作用。代码很简单:这是布局:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<TextView 
    android:id="@+id/text"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:text="Hello"/>

<Button 
    android:id="@+id/trigger"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Press Me"/>

</LinearLayout>

这是 Java 代码:

private int buttonPress = 0;
TextView mButtonLabel;

private long mStartTime = 0L;
TextView mTimeLabel;

private Handler mHandler = new Handler();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if(mStartTime == 0L) {
        mStartTime = SystemClock.uptimeMillis();
        mHandler.removeCallbacks(mUpdateTimeTask);
        mHandler.postDelayed(mUpdateTimeTask, 100);
    }

    mTimeLabel = (TextView)findViewById(R.id.text);
    mButtonLabel = (TextView)findViewById(R.id.trigger);

    Button startButton = (Button)findViewById(R.id.trigger);

    startButton.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            mButtonLabel.setText("Megnyomva: " + ++buttonPress + " alkalommal");
        }
    });
}

private Runnable mUpdateTimeTask = new Runnable() {
    public void run() {
        final long start = mStartTime;
        long milis = SystemClock.uptimeMillis() - start;
        int seconds = (int) (milis/1000);
        int minutes = (seconds/60);
        seconds = seconds % 60;

        mTimeLabel.setText("" + minutes + ":" + String.format("%02d", seconds));
        mHandler.postDelayed(this, 200);
    }
};

@Override
protected void onPause() {
    mHandler.removeCallbacks(mUpdateTimeTask);
    super.onPause();
}

@Override
protected void onResume() {
    super.onResume();
    mHandler.postDelayed(mUpdateTimeTask, 100);
}

我的问题是，该按钮不知何故不可见。有什么建议吗？

谢谢，戴夫。

Answer 1

来自

<LinearLayout 
 xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:orientation="vertical" >

<TextView 
 android:id="@+id/text"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:text="Hello"/>

<Button 
 android:id="@+id/trigger"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text="Press Me"/>

</LinearLayout>

至

<RelativeLayout 
 xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:orientation="vertical" >

<TextView 
 android:id="@+id/text"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:text="Hello"/>

<Button 
 android:id="@+id/trigger"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text="Press Me"/>

</RelativeLayout >