Android下利用Bitmap切割图片

在自己自定义的一个组件中由于需要用图片显示数字编号，而当前图片就只有一张，上面有0-9是个数字，于是不得不考虑将其中一个个的数字切割下来，需要显示什么数字，只需要组合一下就好了。
下面是程序的关键代码：
在MyView（继承于View）类中的重写的onDraw(Canvas canvas)方法中，有如下代码段：

Bitmap resource = BitmapFactory.decodeResource(this.getResources(), R.drawable.num);  Bitmap zero = Bitmap.createBitmap(resource, 0, 0, 12, 12);  Bitmap one = Bitmap.createBitmap(resource, 12, 0, 12, 12);  Bitmap two = Bitmap.createBitmap(resource, 24, 0, 12, 12);  Bitmap three = Bitmap.createBitmap(resource, 36, 0, 12, 12);  Bitmap four = Bitmap.createBitmap(resource, 48, 0, 12, 12);  Bitmap five = Bitmap.createBitmap(resource, 60, 0, 12, 12);  Bitmap six = Bitmap.createBitmap(resource, 72, 0, 12, 12);  Bitmap seven = Bitmap.createBitmap(resource, 84, 0, 12, 12);  Bitmap eight = Bitmap.createBitmap(resource, 96, 0, 12, 12);  Bitmap nine = Bitmap.createBitmap(resource, 108, 0, 12, 12);

其中R.drawable.num为数字图片，每个数字占据的像素为12*12，Bitmap.createBitmap方法中的五个参数意义分别为：需要切割的图片资源、切割起始点的X坐标、切割起始点的Y坐标、切割多宽、切割多高。
切割下来之后就非常简单的就可以显示各种数字了，例如：用String类型的number表示需要显示的数字，则

char nums[] = number.toCharArray();  for(int i = 0; i < nums.length; i ++) {  if(nums[i] == '0') {  canvas.drawBitmap(zero, i * 12, 0, mPaint);  } else if(nums[i] == '1') {  canvas.drawBitmap(one, i * 12, 0, mPaint);  } else if(nums[i] == '2') {  canvas.drawBitmap(two, i * 12, 0, mPaint);  } else if(nums[i] == '3') {  canvas.drawBitmap(three, i * 12, 0, mPaint);  } else if(nums[i] == '4') {  canvas.drawBitmap(four, i * 12, 0, mPaint);  } else if(nums[i] == '5') {  canvas.drawBitmap(five, i * 12, 0, mPaint);  } else if(nums[i] == '6') {  canvas.drawBitmap(six, i * 12, 0, mPaint);  } else if(nums[i] == '7') {  canvas.drawBitmap(seven, i * 12, 0, mPaint);  } else if(nums[i] == '8') {  canvas.drawBitmap(eight, i * 12, 0, mPaint);  } else if(nums[i] == '9') {  canvas.drawBitmap(nine, i * 12, 0, mPaint);  }  }

其中canvas为画布，drawBitmap方法中的四个参数的意义分别为：需要绘制的图片资源、在画布上绘制的起始点的X坐标、Y坐标、画笔。其中画笔在此处可以不进行任何设置，只需new一个出来即可，Paint mPaint = new Paint();

完整代码

NumView

package com.barney;import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.DisplayMetrics;
import android.view.View;public class NumView extends View {private static Paint mPaint;private String num;public NumView(Context context, String num) {super(context);this.num = num;mPaint = new Paint();}@Overridepublic void draw(Canvas canvas) {super.onDraw(canvas);int base = 0;mPaint.setAntiAlias(true);DisplayMetrics dm = new DisplayMetrics();  dm = getResources().getDisplayMetrics(); BitmapFactory.Options options = new BitmapFactory.Options();options.inDensity = dm.densityDpi;Bitmap resource = BitmapFactory.decodeResource(this.getResources(), R.drawable.num, options);Bitmap zero = Bitmap.createBitmap(resource, 0, 0, 12, 12);Bitmap one = Bitmap.createBitmap(resource, 12, 0, 12, 12);Bitmap two = Bitmap.createBitmap(resource, 24, 0, 12, 12);Bitmap three = Bitmap.createBitmap(resource, 36, 0, 12, 12);Bitmap four = Bitmap.createBitmap(resource, 48, 0, 12, 12);Bitmap five = Bitmap.createBitmap(resource, 60, 0, 12, 12);Bitmap six = Bitmap.createBitmap(resource, 72, 0, 12, 12);Bitmap seven = Bitmap.createBitmap(resource, 84, 0, 12, 12);Bitmap eight = Bitmap.createBitmap(resource, 96, 0, 12, 12);Bitmap nine = Bitmap.createBitmap(resource, 108, 0, 12, 12);char nums[] = num.toCharArray();for(int i = 0; i < nums.length; i ++) {Rect rect = new Rect();rect.set(base + i * 12, 0, base + i * 12 + 12, 12);Bitmap bitmap = null;if(nums[i] == '0') {bitmap = zero;} else if(nums[i] == '1') {bitmap = one;} else if(nums[i] == '2') {bitmap = two;} else if(nums[i] == '3') {bitmap = three;} else if(nums[i] == '4') {bitmap = four;} else if(nums[i] == '5') {bitmap = five;} else if(nums[i] == '6') {bitmap = six;} else if(nums[i] == '7') {bitmap = seven;} else if(nums[i] == '8') {bitmap = eight;} else if(nums[i] == '9') {bitmap = nine;}canvas.drawBitmap(bitmap,null, rect, mPaint);}}
}

BitmapDemoActivity

package com.barney;import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;public class BitmapDemoActivity extends Activity {private EditText myEditText;private Button myButton;private LinearLayout myLinearLayout;/** Called when the activity is first created. */@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);myButton = (Button) this.findViewById(R.id.myButton);myEditText = (EditText) this.findViewById(R.id.myEditText);myLinearLayout = (LinearLayout) this.findViewById(R.id.myLinearLayout);myButton.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubString num = myEditText.getText().toString();NumView numView = new NumView(BitmapDemoActivity.this, num);myLinearLayout.removeAllViews();myLinearLayout.addView(numView);}});}
}