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();
}
@Override
public 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. */
@Override
public 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() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
String num = myEditText.getText().toString();
NumView numView = new NumView(BitmapDemoActivity.this, num);
myLinearLayout.removeAllViews();
myLinearLayout.addView(numView);
}
});
}
}源代码
参考链接
Android下利用Bitmap切割图片 - - ITeye技术网站