Java 为什么我的观点没有改变?
我有以下代码:Java 为什么我的观点没有改变?,java,android,Java,Android,我有以下代码: public class DrawView extends View { Paint paint = new Paint(); public DrawView(Context context) { super(context); } @Override public void onDraw(Canvas canvas) { paint.setColor(Color.BLACK);
public class DrawView extends View {
Paint paint = new Paint();
public DrawView(Context context) {
super(context);
}
@Override
public void onDraw(Canvas canvas) {
paint.setColor(Color.BLACK);
paint.setStrokeWidth(3);
canvas.drawRect(30, 30, 80, 80, paint);
paint.setStrokeWidth(0);
paint.setColor(Color.CYAN);
canvas.drawRect(33, 60, 77, 77, paint );
paint.setColor(Color.YELLOW);
canvas.drawRect(33, 33, 77, 60, paint );
}
}
主要课程包括:
public class MainActivity extends Activity {
DrawView drawView;
Button btn;
View view;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn = (Button) findViewById(R.id.button1);
view = (View) findViewById(R.id.view1);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
generate();
}
});
}
public void generate() {
drawView = new DrawView(this);
drawView.setBackgroundColor(Color.WHITE);
view = drawView;
}
}
问题是:当我点击按钮时,我看不到绘图视图,我不知道为什么
编辑:以下是xml代码:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/root"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<Button
android:id="@+id/button1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/generate" />
<View
android:id="@+id/view1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
使用addView方法将在generate()方法中创建的新视图添加到“活动”视图中。您需要通过XML或代码将自定义视图添加到视图层次结构中。您必须通过addView方法将DrawView添加到某个视图组父视图R.layout.activity\u main已具有视图视图;在其xml代码中,但您正在创建一个drawView=新的drawView(this);这是一个从未添加过的新视图。您需要添加此视图以使其可见