如何在我的 Android 应用程序中实现 ScrollImageView 类

Question

我找到了这个类：

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;


// borrowed from https://sites.google.com/site/androidhowto/how-to-1/custom-scrollable-image-view
public class ScrollImageView extends View {
    private final int DEFAULT_PADDING = 10;
    private Display mDisplay;
    private Bitmap mImage;

    /* Current x and y of the touch */
    private float mCurrentX = 0;
    private float mCurrentY = 0;

    private float mTotalX = 0;
    private float mTotalY = 0;
    /* The touch distance change from the current touch */
    private float mDeltaX = 0;
    private float mDeltaY = 0;

    int mDisplayWidth;
    int mDisplayHeight;
    int mPadding;

    public ScrollImageView(Context context) {
        super(context);
        initScrollImageView(context);
    }

    public ScrollImageView(Context context, AttributeSet attributeSet) {
        super(context);
        initScrollImageView(context);
    }

    private void initScrollImageView(Context context) {
        mDisplay = ((WindowManager)context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
        mPadding = DEFAULT_PADDING;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int width = measureDim(widthMeasureSpec, mDisplay.getWidth());
        int height = measureDim(heightMeasureSpec, mDisplay.getHeight());
        setMeasuredDimension(width, height);
    }

    private int measureDim(int measureSpec, int size) {
        int result = 0;
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);

        if (specMode == MeasureSpec.EXACTLY) {
            result = specSize;
        } else {
            result = size;
            if (specMode == MeasureSpec.AT_MOST) {
               result = Math.min(result, specSize);
            }
        }
        return result;
    }

    public Bitmap getImage() {
        return mImage;
    }

    public void setImage(Bitmap image) {
        mImage = image;
    }

    public int getPadding() {
        return mPadding;
    }

    public void setPadding(int padding) {
        this.mPadding = padding;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (event.getAction() == MotionEvent.ACTION_DOWN) {
            mCurrentX = event.getRawX();
            mCurrentY = event.getRawY();
        } 
        else if (event.getAction() == MotionEvent.ACTION_MOVE) {
            float x = event.getRawX();
            float y = event.getRawY();

            // Update how much the touch moved
            mDeltaX = x - mCurrentX;
            mDeltaY = y - mCurrentY;

            mCurrentX = x;
            mCurrentY = y;

            invalidate();
        }
        // Consume event
        return true;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (mImage == null) {
            return;
        }

        float newTotalX = mTotalX + mDeltaX;

        // Don't scroll off the left or right edges of the bitmap.
        if (mPadding > newTotalX && newTotalX > getMeasuredWidth() - mImage.getWidth() - mPadding)
            mTotalX += mDeltaX;

        float newTotalY = mTotalY + mDeltaY;

        // Don't scroll off the top or bottom edges of the bitmap.
        if (mPadding > newTotalY && newTotalY > getMeasuredHeight() - mImage.getHeight() - mPadding)
            mTotalY += mDeltaY;

        Paint paint = new Paint();
        canvas.drawBitmap(mImage, mTotalX, mTotalY, paint);
    }
}

并且很困惑如何在我的应用程序中使用它。

我希望我的应用程序在横向时显示可垂直和水平滚动的位图图像。我从 URL 中提取图像并以编程方式将其设为位图。我调用一个返回位图图像的方法。

有什么想法吗？

Answer 1

setImage 方法采用位图。因此，您应该能够在活动中以编程方式创建此视图，使用位图设置图像并将视图放入布局中。

我以前从未见过这门课，所以你的情况可能会有所不同;)