在自己自定義的一個組件中由于需要用圖片顯示數字編號，而當前圖片就只有一張，上面有0-9是個數字，于是不得不考慮將其中一個個的數字切割下來，需要顯示什么數字，只需要組合一下就好了。
下面是程序的關鍵代碼：
在MyView（繼承于View）類中的重寫的onDraw(Canvas canvas)方法中，有如下代碼段：

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為數字圖片，每個數字占據的像素為12*12，Bitmap.createBitmap方法中的五個參數意義分別為：需要切割的圖片資源、切割起始點的X坐標、切割起始點的Y坐標、切割多寬、切割多高。
切割下來之后就非常簡單的就可以顯示各種數字了，例如：用String類型的number表示需要顯示的數字，則

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為畫布，drawBitmap方法中的四個參數的意義分別為：需要繪制的圖片資源、在畫布上繪制的起始點的X坐標、Y坐標、畫筆。其中畫筆在此處可以不進行任何設置，只需new一個出來即可，Paint mPaint = new Paint();

完整代碼

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);}});} }

源代碼

源代碼

參考鏈接

Android下利用Bitmap切割圖片 - - ITeye技術網站

效果如下

總結

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