Android開發經驗之在圖片上隨意點擊移動文字

只要在圖片范圍之內，文字可隨意點擊移動。

package xiaosi.GetTextImage;


import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;

public class GetTextImage extends View
{
    private float x = 20, y = 40;
    private static float windowWidth;
    private static float windowHeight;
    private static float left = 0;      //圖片在屏幕中位置X坐標
    private static float top = 0;       //圖片在屏幕中位置Y坐標
    private String str = "我愛你";
    private DisplayMetrics dm = new DisplayMetrics();  //用于獲取屏幕的高度和寬度
    private WindowManager windowManager;
    private Bitmap newbitmap;

    public GetTextImage(Context context)
    {
        super(context);
        windowManager = (WindowManager) context
                .getSystemService(Context.WINDOW_SERVICE);
        //屏幕的寬度
        windowWidth = windowManager.getDefaultDisplay().getWidth();
        //屏幕的高度
        windowHeight = windowManager.getDefaultDisplay().getHeight();
    }

    public void onDraw(Canvas canvas)
    {
        Resources res = getResources();
        Bitmap bmp = BitmapFactory.decodeResource(res, R.drawable.b);
        newbitmap = getTextImage(bmp, str, x, y);
        canvas.drawBitmap(newbitmap, 0, 0, null);
    }
    /**
     * 返回值: Bitmap 參數：原圖片,文字 功能: 根據給定的文字生成相應圖片
     * 
     * @param originalMap 
     * @param text  文字
     * @param x  點擊的X坐標
     * @param y  點擊的Y坐標
     * @return
     */
    public static Bitmap getTextImage(Bitmap originalMap, String text, float x,
            float y)
    {
        float bitmapWidth = originalMap.getWidth();
        float bitmapHeight = originalMap.getHeight();
        // 定義畫布
        Canvas canvas = new Canvas(originalMap);
        // 定義畫筆
        Paint paint = new Paint();
        //獲得文本的長度（像素）
        float textWidth = paint.measureText(text); 
        canvas.drawBitmap(originalMap, 0, 0, null);

        // 如果圖片寬度小于屏幕寬度
        if (left + bitmapWidth < windowWidth)
        {
            // 右邊界
            if (x >= left + bitmapWidth - textWidth)
            {
                x = left + bitmapWidth - textWidth;
            }
            // 左邊界
            else if (x <= left)
            {
                x = left;
            }
        }
        else
        {
            // 右邊界
            if (x >= windowWidth - textWidth)
            {
                x = windowWidth - textWidth;
            }
            // 左邊界
            else if (x <= 0)
            {
                x = 0;
            }
        }
        // 如果圖片高度小于屏幕高度
        if (top + bitmapHeight < windowHeight)
        {
            // 下
            if (y >= top + bitmapHeight)
            {
                y = top + bitmapHeight;
            }
            // 上
            else if (y <= top + 10)
            {
                y = top + 10;
            }
        }
        else
        {
            if (y >= windowHeight)
            {
                y = windowHeight;
            }
            else if (y <= 0)
            {
                y = 0;
            }
        }

        // 添加字
        canvas.drawText(text, x, y, paint);
        return originalMap;
    }
    @Override
    public boolean onTouchEvent(MotionEvent event)
    {
        if (event.getAction() == MotionEvent.ACTION_DOWN)
        {
            x = event.getX();
            y = event.getY();
            // 重繪
            invalidate();
        }
        return true;
    }
}

package xiaosi.GetTextImage;

import android.app.Activity;
import android.os.Bundle;

public class GetTextImageActivity extends Activity {
    /** Called when the activity is first created. */
    private GetTextImage get;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        get = new GetTextImage(this);
        setContentView(get);
    }
}