android - 如何在 Android 中创建一个半圆形的 imageview

Question

我想创建一个半圆/圆形 ImageView 。下面是我用来创建圆形 ImageView 的代码，但我无法创建半圆形图像(半圆)

package com.example.dynamicviews;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Shader;
import android.graphics.drawable.BitmapDrawable;
import android.util.AttributeSet;
import android.widget.ImageView;

/**
 * Customized Imageview with Rounded Border and Shadow
 * @author Rahul Gupta <rahulg@exzeo.com>
 * @since 2014-01-01
 */
public class RoundedImageView extends ImageView
{
    private int borderWidth = 2;
    private int viewWidth;
    private int viewHeight;
    private Bitmap image;
    private Paint paint;
    private Paint paintBorder;
    private BitmapShader shader;

    public RoundedImageView(Context context)
    {
        super(context);
        setup();
    }

    public RoundedImageView(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        setup();
    }

    public RoundedImageView(Context context, AttributeSet attrs, int defStyle)
    {
        super(context, attrs, defStyle);
        setup();
    }

    /**
     * Custom Class to round imageview with color
     * @param context Context of the activity
     * @param borderColor Border color to be set
     */
    @SuppressLint("NewApi")
    public RoundedImageView(Context context, String borderColor) {
        super(context);
         // init paint
        paint = new Paint();
        paint.setAntiAlias(true);
        paintBorder = new Paint();
        setBorderColor(Color.WHITE);
        paintBorder.setAntiAlias(true);
        this.setLayerType(LAYER_TYPE_SOFTWARE, paintBorder);
        paintBorder.setShadowLayer(3.0f, 0.0f,1.0f, Color.parseColor(borderColor));
    }

    @SuppressLint("NewApi")
    private void setup()
    {
        // init paint
        paint = new Paint();
        paint.setAntiAlias(true);
        paintBorder = new Paint();
        setBorderColor(Color.WHITE);
        paintBorder.setAntiAlias(true);
        this.setLayerType(LAYER_TYPE_SOFTWARE, paintBorder);
        paintBorder.setShadowLayer(3.0f, 0.0f,1.0f, Color.BLACK);
        loadBitmap();
    }

    public void setBorderWidth(int borderWidth)
    {
        this.borderWidth = borderWidth;
        this.invalidate();
    }

    public void setBorderColor(int borderColor)
    {
        if (paintBorder != null)
            paintBorder.setColor(borderColor);

        this.invalidate();
    }

    private void loadBitmap()
    {
        BitmapDrawable bitmapDrawable = (BitmapDrawable) this.getDrawable();

        if (bitmapDrawable != null)
            image = bitmapDrawable.getBitmap();
    }

    @SuppressLint("DrawAllocation")
    @Override
    public void onDraw(Canvas canvas)
    {
        // load the bitmap

        // init shader
        if (image != null)
        {
            shader = new BitmapShader(Bitmap.createScaledBitmap(image, canvas.getWidth(), canvas.getHeight(), false), Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
            paint.setShader(shader);
            int circleCenter = viewWidth / 2;

            // circleCenter is the x or y of the view's center
            // radius is the radius in pixels of the cirle to be drawn
            // paint contains the shader that will texture the shape
            canvas.drawCircle(circleCenter + borderWidth, circleCenter + borderWidth, circleCenter + borderWidth - 4.0f, paintBorder);
            canvas.drawCircle(circleCenter + borderWidth, circleCenter + borderWidth, circleCenter - 4.0f, paint);
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        int width = measureWidth(widthMeasureSpec);
        int height = measureHeight(heightMeasureSpec, widthMeasureSpec);

        viewWidth = width - (borderWidth * 2);
        viewHeight = height - (borderWidth * 2);

        setMeasuredDimension(width, height);
    }

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

        if (specMode == MeasureSpec.EXACTLY)
        {
            // We were told how big to be
            result = specSize;
        }
        else
        {
            // Measure the text
            result = viewWidth;
        }

        return result;
    }

    private int measureHeight(int measureSpecHeight, int measureSpecWidth)
    {
        int result = 0;
        int specMode = MeasureSpec.getMode(measureSpecHeight);
        int specSize = MeasureSpec.getSize(measureSpecHeight);

        if (specMode == MeasureSpec.EXACTLY)
        {
            // We were told how big to be
            result = specSize;
        }
        else
        {
            // Measure the text (beware: ascent is a negative number)
            result = viewHeight;
        }

        return (result + 2);
    }
}

这是它的截图:-

期望的结果如下所示:- 两个 ImageView 的左半圆和右半圆，中间有图像资源:-

Answer 1

我的一个项目有相同的半圆，里面需要显示一些图像，所以我只是使用简单的技巧，我只是创建一个半圆图像并设置为 ImageView 的 src，然后我将另一张图像设置为背景。你也可以有一些技巧，比如创建简单的框架布局并将一些半圆形图像设置为背景，并在该框架布局的一侧使用一些 ImageView 并将其他图像设置为该 ImageView 。我希望这可以为您提供一些完成任务的基本思路。祝你好运:)