Question

我几乎是Android开发的新手。我尝试根据触摸事件绘制线条。它适用于滚动视图。但是，当我使用scrollView时，它只是不起作用。我在其他帖子中读到了一些问题和答案，但没有什么能让我理解代码应该如何。

这是我的代码：

public class CustomDrawingView extends View 
{
    private final int paintColor = Color.BLACK;
    private Paint drawPaint;
    private Path path = new Path();
    private boolean clearCanvas = false;

public CustomDrawingView(Context context, AttributeSet attrs)
{
    super (context, attrs);
    setupPaint();
}

private void setupPaint() {
    drawPaint = new Paint();
    drawPaint.setColor(paintColor);
    drawPaint.setAntiAlias(true);
    drawPaint.setStrokeWidth(5);
    drawPaint.setStyle(Paint.Style.STROKE);
    drawPaint.setStrokeJoin(Paint.Join.ROUND);
    drawPaint.setStrokeCap(Paint.Cap.ROUND);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
    float touchX = event.getX();
    float touchY = event.getY();
    switch (event.getAction())
    {
        case MotionEvent.ACTION_DOWN:
            path.moveTo(touchX, touchY);
            break;
        case MotionEvent.ACTION_MOVE:
            path.lineTo(touchX, touchY);
            break;
    }
    postInvalidate();
    return true;
}
@Override
protected void onDraw(Canvas canvas) {
    canvas.drawPath(path, drawPaint);
}
public void clearScreen()
{
    path.reset();
    postInvalidate();
}

}

MainActifity：

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.mirana.touchinteraction.MainActivity">

    <ScrollView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">

        <com.example.mirana.touchinteraction.CustomDrawingView
            android:id="@+id/simpleDrawingView1"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            />
    </ScrollView>

</RelativeLayout>

如何根据触摸交互在屏幕上绘制线条？请帮帮我。

在下图中，屏幕包含“工作绘制”是我想要运行的代码（从xml中删除scrollView）。当我将scrollview添加到xml时，就像上面的代码一样，空白屏幕就是结果。我可以通过触摸绘制任何东西并将指针拖到屏幕上。

"working" screen and "not working" screen captures

添加customDrawingview ino scrollView

0 个答案: