android 画图之bitmap(一)
16lz
2021-01-25
要把一个Bitmap画到View上,必须用到的类有android.graphics.Canvas,和android.graphics.Bitmap。方法很简单,在View里面,重载onDraw(Canvascanvas)方法,然后用canvas.drawBitmap()方法,将其画在屏幕上。
代码:
public class ViewActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(new MyView(this)); } public class MyView extends View { private Bitmap mBitmap; private int mScreenWidth; private int mScreenHeight; public MyView(Context context) { super(context); initialize(); } private void initialize() { DisplayMetrics dm = getResources().getDisplayMetrics(); mScreenWidth = dm.widthPixels; mScreenHeight = dm.heightPixels; // Bitmap bmp mBitmap = ((BitmapDrawable)getResources().getDrawable(R.drawable.show)).getBitmap();// mBitmap = Bitmap.createScaledBitmap(bmp, mScreenWidth, mScreenHeight, true); } @Override protected void onDraw(Canvas canvas) {// super.onDraw(canvas); //当然,如果界面上还有其他元素需要绘制,只需要将这句话写上就行了。 canvas.drawBitmap(mBitmap, 0, 0, null); } }}
原图:
程序里显示效果:
现在我们来做点效果:
上面是直接将原图画在屏幕上,没有任何处理,我们试着将图片拉伸以填满整个屏幕。(电脑桌面有平铺,拉伸,居中等操作)
代码:
public class ViewActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(new MyView(this)); } public class MyView extends View { private Bitmap mBitmap; private int mScreenWidth; private int mScreenHeight; public MyView(Context context) { super(context); initialize(); } private void initialize() { DisplayMetrics dm = getResources().getDisplayMetrics(); mScreenWidth = dm.widthPixels; mScreenHeight = dm.heightPixels; Bitmap bmp = ((BitmapDrawable)getResources().getDrawable(R.drawable.show)).getBitmap(); mBitmap = Bitmap.createScaledBitmap(bmp, mScreenWidth, mScreenHeight, true); } @Override protected void onDraw(Canvas canvas) {// super.onDraw(canvas); //当然,如果界面上还有其他元素需要绘制,只需要将这句话写上就行了。 canvas.drawBitmap(mBitmap, 0, 0, null); } }}
是不是拉伸了啊,铺满了整个屏幕啊
参考资料:
http://chroya.iteye.com/blog/710210
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