自定义视图onDraw方法不绘图

时间：2015-11-20 01:58:01

标签： android

我正在为学校的团队项目和onDraw方法开发一个简单的绘图应用程序，虽然可靠地调用，但只生成一个空白的白色屏幕。这是在我们决定从使用活动切换到碎片之后发生的。当我们在Draw Activity中使用时，我的Drawing View代码工作正常，但是现在我们正在使用DrawFragment，它不起作用。我一直在寻找那些有类似问题的人，但无济于事。最初，我认为这是由于传递给具有空位图的onDraw方法的Canvas参数，但是当我将画布设置为我自己的私有变量mCanvas时，问题仍然存在。

编辑：我忘了提及，当我在调试器中查看代码时，在onDraw方法的末尾，在调完每一行之后，我可以查看画布中包含的位图并查看是完全绿色，并具有我指定的路径。但是，没有任何东西可以进入我设备上的实际屏幕。

EDIT2：用Mike的建议修改了我的fragment_draw.xml，但是我仍然遇到同样的问题。我尝试将RelativeLayout的背景设置为透明，以查看是否会产生影响，但事实并非如此。

我的绘图视图：

package edu.cascadia.doodlebug;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class DrawingView extends View {

    private final int TOUCH_TOLERANCE = 4;

    private float mX, mY; // coordinates for tracking path drawing
    private Bitmap mBitmap; // bitmap for the canvas
    private Canvas mCanvas; // canvas object to draw onto
    private Path mPath; // path for drawing
    private Paint mPaint; // paint to describe the line being drawn
    private Paint mBitmapPaint;
    private Context mContext;

public DrawingView(Context c) {
    this(c, null);
}

public DrawingView(Context c, AttributeSet attr) {
    super(c, attr);
    mContext = c;
    mPath = new Path();

    setWillNotDraw(false);
    setWillNotCacheDrawing(false);

    // set up paint object for the line
    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(Color.BLACK);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(12);

    // bitmap paint to draw bitmap
    mBitmapPaint = new Paint();
}

@Override
protected void onSizeChanged(int w, int h, int oldW, int oldH) {
    super.onSizeChanged(w, h, oldW, oldH);
    mBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
    mCanvas = new Canvas(mBitmap);
}

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

    canvas.drawColor(Color.GREEN);

    // Test Code
    mPath.reset();
    mPath.moveTo(0, 0);
    mPath.lineTo(300, 500);
    mPath.quadTo(300, 500, 330, 750);
    mPath.lineTo(getWidth(), getHeight());
    mPath.close();

    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);

    canvas.drawPath(mPath, mPaint);
}

@Override
public boolean onTouchEvent(MotionEvent event) {

    final float x = event.getX();
    final float y = event.getY();

    switch (event.getActionMasked()) {
        case MotionEvent.ACTION_DOWN:
        case MotionEvent.ACTION_POINTER_DOWN:
            touchStart(x, y);
            invalidate();
            break;
        case MotionEvent.ACTION_MOVE:
            touchMove(x, y);
            invalidate();
            break;
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_POINTER_UP:
            touchEnd();
            invalidate();
            break;
    }

    return true;
}

private void touchStart(float x, float y) {

    // set up the path to start drawing from this location
    mPath.reset();
    mPath.moveTo(x, y);

    // add the start coordinates
    mX = x;
    mY = y;
}

private void touchMove(float x, float y) {
    // get the change in both x and y directions
    float deltaX = Math.abs(x - mX);
    float deltaY = Math.abs(y - mY);

    // check if greater than touch tolerance
    if (deltaX >= TOUCH_TOLERANCE || deltaY >= TOUCH_TOLERANCE) {
        //draw the line to the new coordinates
        mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
        mX = x;
        mY = y;
    }
}

private void touchEnd() {
    mPath.lineTo(mX, mY);
    mCanvas.drawPath(mPath, mPaint);
    mPath.close();
    mPath.reset();
}

public int getLineWidth() {
    return (int) mPaint.getStrokeWidth();
}

public void setLineWidth(int width) {
    mPaint.setStrokeWidth(width);
}

public void setBackground(Bitmap bitmap) {
    mCanvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
}
}

我的DrawFragment：

package edu.cascadia.doodlebug;

import android.app.Activity;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class DrawFragment extends Fragment {
    private OnFragmentInteractionListener mListener;
    private DrawingView mView;

public DrawFragment() {}

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

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View v = inflater.inflate(R.layout.fragment_draw, container, false);
    mView = (DrawingView) v.findViewById(R.id.drawingView);
    return v;
}

public void setBackground(Bitmap bitmap) { mView.setBackground(bitmap); }

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    try {
        mListener = (OnFragmentInteractionListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
}

public interface OnFragmentInteractionListener {
    void startCamera();
}
}

编辑：更新了fragment_draw.xml：

<RelativeLayout 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" tools:context="edu.cascadia.doodlebug.DrawFragment"
android:background="#ffff">


<view
    android:id="@+id/drawingView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:visibility="visible"
    class="edu.cascadia.doodlebug.DrawingView" />

<ImageView
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:id="@+id/imageView"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:src="@drawable/color_selector"
    android:contentDescription=""/>

<LinearLayout
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:id="@+id/linearLayout">

    <ImageView
        android:layout_width="48dp"
        android:layout_height="50dp"
        android:id="@+id/imgBee"
        android:src="@drawable/bee_sticker" />

    <ImageView
        android:layout_width="48dp"
        android:layout_height="50dp"
        android:id="@+id/imgDinosaur"
        android:src="@drawable/dinosaur_sticker" />

    <ImageView
        android:layout_width="48dp"
        android:layout_height="50dp"
        android:id="@+id/imgKitty"
        android:src="@drawable/kitty_sticker" />

    <ImageView
        android:layout_width="48dp"
        android:layout_height="50dp"
        android:id="@+id/imgTaz"
        android:src="@drawable/taz_sticker" />

    <ImageView
        android:layout_width="48dp"
        android:layout_height="50dp"
        android:id="@+id/imgLego"
        android:src="@drawable/lego_sticker" />

    <ImageView
        android:layout_width="48dp"
        android:layout_height="50dp"
        android:id="@+id/imgTurkey"
        android:src="@drawable/turkey_sticker" />
</LinearLayout>

<ImageButton
    android:layout_width="70dp"
    android:layout_height="55dp"
    android:id="@+id/imageButttonTakePic"
    android:src="@drawable/camera"
    android:layout_toRightOf="@+id/imageView"
    android:scaleType="fitXY"
    android:layout_marginLeft="20dp" />
</RelativeLayout>

1 个答案:

答案 0 :(得分：0)

我也遇到了这个问题，就我而言，我要做的就是将背景设置为某种东西。 

    <com.microdevrj.hydrogenrecyclerview.HydrogenRV
    android:id="@+id/hydro"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/transparent" />
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