Android Studio：创建签名的 apk 时出错

Question

我在尝试生成签名的 APK 时不断收到此错误

Error:Error: This class should provide a default constructor (a public constructor with no arguments) (com.STMReport.Viewer.FirmaDigital) [Instantiatable]

任何人都可以帮助我就造成这种情况的原因提供一些建议吗？我调查了这个问题，它与默认构造函数上的 super() 有关，但是当我尝试删除这行代码时，它给了我另一个错误

Error:(24, 42) error: no suitable constructor found for View(no arguments)
constructor View.View(Context) is not applicable

这是我的课：

package com.STMReport.Viewer;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;

import android.view.MotionEvent;
import android.view.View;


public class FirmaDigital extends View {

private Bitmap mBitmap;
private Canvas  mCanvas;
private Path    mPath;
private Paint   mBitmapPaint;
private Paint   mPaint;
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;


public FirmaDigital(Context context) {
    super(context);

    mPath = new Path();
    mBitmapPaint = new Paint(Paint.DITHER_FLAG);

    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(0xFF000000);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(3);
}
@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) {
    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);

    canvas.drawPath(mPath, mPaint);
}

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

private void touch_mover(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;
    }
}

private void touch_ups() {
    mPath.lineTo(mX, mY);
    // 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_starto(x, y);
            invalidate();
            break;
        case MotionEvent.ACTION_MOVE:
            touch_mover(x, y);
            invalidate();
            break;
        case MotionEvent.ACTION_UP:
            touch_ups();
            invalidate();
            break;
    }
 return true;
}

}

我忘了添加我是如何使用这个类的：

public class FirmaActivity extends Activity {

RelativeLayout parent;
FirmaDigital firma;
@Override

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_firma);
    parent = (RelativeLayout)findViewById(R.id.FirmaLayout);
    firma = new FirmaDigital(this);
    parent.addView(firma);
}
}

任何帮助将不胜感激 谢谢！

Answer 1

我相信你应该提供一个以 Context 和 AttributeSet 作为参数的构造函数

public yourClass(Context context, AttributeSet attrs){
   super(context,attrs);
  // Your implementation
}

你可以参考这个链接http://developer.android.com/training/custom-views/create-view.html

Answer 2

尝试在自定义视图中定义构造函数：

    public FirmaDigital(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    public FirmaDigital(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public FirmaDigital(Context context) {
        super(context);
        init();
    }

    public void init(){
        mPath = new Path();
        mBitmapPaint = new Paint(Paint.DITHER_FLAG);

        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(0xFF000000);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(3);
    }