Question

我想创建一个绘图应用程序。为此，我创建了一个Custom DrawingView。要在绘图期间启用其他选项，CustomView应包含在特定区域的activity_main.xml中。

 CGRect circleRect = CGRectMake(circles[i][0] - circles[i][2] ,
                                circles[i][1] - circles[i][2],
                                2 * circles[i][2],
                                2 * circles[i][2]
                           );

public class MainActivity extends AppCompatActivity {

DrawingView dv ;
private Paint mPaint;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(Color.GREEN);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(12);

    dv = new DrawingView(this, mPaint);
    setContentView(R.layout.activity_main);
} 
}

＆＃13;

public class DrawingView extends View {

public int width;
public  int height;
private Bitmap mBitmap;
private Canvas  mCanvas;
private Path    mPath;
private Paint   mBitmapPaint, mPaint;
Context context;
private Paint circlePaint;
private Path circlePath;

public DrawingView(Context c, Paint pPaint) {
    super(c);
    context=c;

    mPaint = pPaint;
    mPath = new Path();
    mBitmapPaint = new Paint(Paint.DITHER_FLAG);
    circlePaint = new Paint();
    circlePath = new Path();
    circlePaint.setAntiAlias(true);
    circlePaint.setColor(Color.BLUE);
    circlePaint.setStyle(Paint.Style.STROKE);
    circlePaint.setStrokeJoin(Paint.Join.MITER);
    circlePaint.setStrokeWidth(4f);
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);

    mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    mCanvas = new Canvas(mBitmap);
}

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

    canvas.drawBitmap( mBitmap, 0, 0, mBitmapPaint);
    canvas.drawPath( mPath,  mPaint);
    canvas.drawPath( circlePath,  circlePaint);
}

private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;

private void touch_start(float x, float y) {
    mPath.reset();
    mPath.moveTo(x, y);
    mX = x;
    mY = y;
}

private void touch_move(float x, float y) {
    float dx = Math.abs(x - mX);
    float dy = Math.abs(y - mY);
    if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
        mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
        mX = x;
        mY = y;

        circlePath.reset();
        circlePath.addCircle(mX, mY, 30, Path.Direction.CW);
    }
}

private void touch_up() {
    mPath.lineTo(mX, mY);
    circlePath.reset();
    // commit the path to our offscreen
    mCanvas.drawPath(mPath,  mPaint);
    // kill this so we don't double draw
    mPath.reset();
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    float x = event.getX();
    float y = event.getY();

    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            touch_start(x, y);
            invalidate();
            break;
        case MotionEvent.ACTION_MOVE:
            touch_move(x, y);
            invalidate();
            break;
        case MotionEvent.ACTION_UP:
            touch_up();
            invalidate();
            break;
    }
    return true;
}
}

＆＃13;

但是如果我尝试这个，总会抛出InflateException

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:gravity="center"
tools:context="de.sentoon.touchtesterv4.MainActivity"
android:orientation="vertical">

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Hello World!" />

<de.sentoon.touchtesterv4.DrawingView
    android:layout_width="match_parent"
    android:layout_height="150sp" />
</LinearLayout>

感谢您的帮助。

Answer 1

引起：java.lang.NoSuchMethodException：[class android.content.Context，interface android.util.AttributeSet]

您尚未声明足够的构造函数。

通常自定义视图至少有2个构造函数。一个接受Context，另一个接受Context和AttributeSet。

public class DravingView extends View {
    public DravingView(final Context context) {
        super(context);
    }

    public DravingView(final Context context, final AttributeSet attrs) {
        super(context, attrs);
    }
}

为什么我需要那个构造函数？

首先解析xml，然后创建相应的类对象。解析布局xml文件后，框架将尝试使用DrawingView中的应用参数为您创建xml对象。这些参数正在通过AttributeSet传递。但只要它在DrawingView类中找不到这样的构造函数，它就会崩溃。

Answer 2

将您的DrawingView构造函数更改为此

public DrawingView(Context c, AttributeSet attr) {
    super(c, attr);
    context=c;
}

将此方法添加到DrawingView类

public void setPaint(Paint pPaint) {
        mPaint = pPaint;
    }

在xml中向图纸视图添加ID <de.sentoon.touchtesterv4.DrawingView android:id="@+id/drawingView" android:layout_width="match_parent" android:layout_height="150sp" />

然后像这样初始化drawingView dv = (DrawingView) findViewById(R.id.drawingView);

然后在Activity中设置你的画颜 dv.setPaint(mPaint);

Android CustomView集成在Fragment中

2 个答案: