android - 如何在 fragment 中绘制？

Question

我已经使用 viewpager 为我的应用程序创建了 Actionbar 并且它工作正常。现在我想在每个 fragment 上绘制一些对象。任何人都可以建议一个关于如何在 fragment 上绘制的好的教程或示例代码。当 myclass 扩展 Activity 时，我可以在我的 View 上绘制对象，但当它扩展 Fragment 时，我不知道该怎么做。

到目前为止我已经尝试过这段代码，但它不起作用

public class MoviesFragment extends Fragment {

ImageView imageView;
Bitmap bitmap; Bitmap bit;
Canvas canvas;
Paint paint;


public class DrawView extends View {
    Paint paint = new Paint();

    public DrawView(Context context) {
        super(context);
        paint.setColor(Color.BLACK);
    }
    public DrawView(Context context, AttributeSet attrs) {
        super(context, attrs);
        paint.setColor(Color.BLACK);
    }
    public DrawView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        paint.setColor(Color.BLACK);
    }

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

        imageView = (ImageView)this.findViewById(R.id.imageView);


        bit= BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
        bitmap=Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        canvas = new Canvas(bitmap);
        canvas.drawBitmap(bitmap,0,0,null);
        paint = new Paint();
        paint.setFlags(Paint.ANTI_ALIAS_FLAG);
        paint.setColor(Color.BLACK);
        paint.setStrokeWidth(3);
        imageView.setImageBitmap(bitmap);
        canvas.drawLine(0, 0, 250, 250, paint);
        canvas.drawLine(50, 0, 0, 50, paint);

imageView.invalidate();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        int parentWidth = MeasureSpec.getSize(widthMeasureSpec);
        int parentHeight = MeasureSpec.getSize(heightMeasureSpec);
        this.setMeasuredDimension(parentWidth, parentHeight);
    }
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    super.onCreateView(inflater, container, savedInstanceState);

    View rootView = inflater.inflate(R.layout.fragment_movies, container, false);


    return rootView;

}





}

Answer 1

这里的 fragment 没有什么特别的。

用 Fragment 编写的代码 -

public class DrawFragment extends Fragment {
    DrawView  drawView;

    public DrawFragment() {
    }

    /**
     * Returns Instance of DrawFragment
     * 
     * @return Instance of DrawFragment
     */
    public static DrawFragment getInstance() {
        DrawFragment fragment = new DrawFragment();
        fragment.setRetainInstance(true);
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View _view = inflater.inflate(R.layout.layout_drawing_fragment,
                container, false);
        //lets keep a reference of DrawView 
        drawView = (DrawView ) _view.findViewById(R.id.drawing);
        return _view;
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

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

    @Override
    public void onDestroy() {
        super.onDestroy();
    }
}

Activity 代码 onCreateView() only-

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_base_activity);
        // set Draw Fragment
        mFragmentManager = getFragmentManager();
        mFragmentTransaction = mFragmentManager.beginTransaction();
        mDrawFragment = DrawFragment.getInstance();
        mFragmentTransaction.add(R.id.frame_drawing, mDrawFragment, "draw");
        mFragmentTransaction.commit();
    }

fragment 的布局 -

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/parent"
    android:layout_width="fill_parent"
    android:layout_height="match_parent" >

    <com.app.widgets.DrawView 
        android:id="@+id/drawing"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_marginBottom="3dp"
        android:layout_marginLeft="5dp"
        android:layout_marginRight="5dp"
        android:layout_marginTop="3dp"
        android:background="@android:color/transparent" >
    </com.app.widgets.DrawView>

</RelativeLayout>

EDIT: Check following links for drawing lines on Canvas -

Android Canvas drawLine

How to draw a line in android