Question

我有一个带有3个ImageView的LinearLayout。每当用户点击ImageView时，我想在ImageView上绘制一个周围的矩形。我知道如何在ImageView上绘制内容，但我想直接在LinearLayout上绘制。

我该怎么做？我已经编写了以下代码：

setContentView(R.id.anaekran2); LinearLayout linLayout = (LinearLayout) findViewById(R.id.layout01);

有类似linLayout.getCanvas()的内容吗？我找不到类似的功能，但我发现了 linLayout.getDrawingCache()。所以，

Bitmap b = linLayout.getDrawingCache(); Canvas c = new Canvas(b); // this line gives an error, why?

Answer 1

您应该创建自定义线性布局。覆盖onDraw线性布局方法可以解决您的问题。这是自定义线性布局代码。

public class CustomLinearLayout extends LinearLayout {

private Paint mPaint;
private int mClickedChild = -1;

public CustomLinearLayout(Context context) {
    super(context);
    setWillNotDraw(false);
    createPaint();
}

public CustomLinearLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
    setWillNotDraw(false);
    createPaint();
}

public CustomLinearLayout(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    setWillNotDraw(false);
    createPaint();
}

@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
    super.onLayout(changed, l, t, r, b);
    initializeChildrenClickEvent();
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    if(mClickedChild != -1){
        View child = getChildAt(mClickedChild);
        canvas.drawRect(child.getLeft(), child.getTop(), child.getRight(), child.getBottom(), mPaint);
    }
}

private void initializeChildrenClickEvent(){
    final int childCount = getChildCount();
    OnClickListener clickListener = new OnClickListener() {
        @Override
        public void onClick(View view) {
            for(int i = 0; i < childCount; i++){
                if(getChildAt(i).equals(view)){
                    mClickedChild = i;
                    break;
                }
            }
            invalidate();
        }
    };

    for(int i = 0; i < childCount; i++){
        getChildAt(i).setOnClickListener(clickListener);
    }
}

private void createPaint(){
    mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setColor(Color.RED);
    mPaint.setStrokeWidth(5f);
}
}

以下是xml中自定义布局的用法。

<CustomLinearLayout      
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="horizontal"
tools:context=".MainActivity">

<ImageView
    android:id="@+id/image_view_1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    android:src="@drawable/ic_launcher" />

<ImageView
    android:id="@+id/image_view_2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    android:src="@drawable/ic_launcher" />

<ImageView
    android:id="@+id/image_view_3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    android:src="@drawable/ic_launcher" />

</CustomLinearLayout>

如何直接绘制到LinearLayout的画布 - Android

1 个答案: