android一些基础功能汇总

lxrlxr 2014-11-03

1.Android开发给图片加边框

http://www.android100.org/html/201303/20/1941.html

2.Android开发之Bitmap图片旋转

http://www.android100.org/html/201303/20/1934.html

3.安卓源码服务专家

http://www.javaapk.com/

http://www.javaapk.com/source/category/demo

4.ImageLoader显示图片

当然可以从sdcard中加载图片。他可以接收的URL有以下几种:
String imageUri = "http://site.com/image.png"; // from Web
String imageUri = "file:///mnt/sdcard/image.png"; // from SD card
String imageUri = "content://media/external/audio/albumart/13"; // from content provider
String imageUri = "assets://image.png"; // from assets
String imageUri = "drawable://" + R.drawable.image; // from drawables (only images, non-9patch)

4.屏幕长亮

方法1:使用PowerManager和WakeLock

InAndroidManifest.xml:

1

<uses-permission android:name="android.permission.WAKE_LOCK" />

在你的activity中:

PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE); 

PowerManager.WakeLock mWakeLock = pm.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "My Tag"); 

// 在 onResume()方法中加入:

mWakeLock.acquire(); //锁住屏幕,使其常亮

//在 onPause() 中加入:

mWakeLock.release();//解锁屏幕。让系统管理屏幕

方法2:使用标志windowflagFLAG_KEEP_SCREEN_ON

@Override 

protected void onCreate(Bundle icicle) { 

    super.onCreate(icicle);

    getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON); 

}

5.Math取整方法

舍掉小数取整:Math.floor(2)=2
舍掉小数取整:Math.floor(2.1)=2
舍掉小数取整:Math.floor(-2.1)=-3
舍掉小数取整:Math.floor(-2.5)=-3
舍掉小数取整:Math.floor(-2.9)=-3
四舍五入取整:Math.rint(2)=2
四舍五入取整:Math.rint(2.1)=2
四舍五入取整:Math.rint(-2.5)=-2
四舍五入取整:Math.rint(2.5)=2
四舍五入取整:Math.rint(2.9)=3
四舍五入取整:Math.rint(-2.9)=-3
四舍五入取整:Math.rint(-2.49)=-2
四舍五入取整:Math.rint(-2.51)=-3
凑整:Math.ceil(2)=2
凑整:Math.ceil(2.1)=3
凑整:Math.ceil(2.5)=3
凑整:Math.ceil(2.9)=3
舍掉小数取整:Math.floor(-2)=-2
舍掉小数取整:Math.floor(-2.1)=-3
舍掉小数取整:Math.floor(-2.5)=-3
舍掉小数取整:Math.floor(-2.9)=-3
凑整:Math.ceil(-2)=-2
凑整:Math.ceil(-2.1)=-2
凑整:Math.ceil(-2.5)=-2
凑整:Math.ceil(-2.9)=-2
Math.round(3.14)3
Math.round(3.5)4
Math.round(-3.14)-3
Math.round(-3.5)-3

总结:floor向下取整,ceil向上取整;round和rint四舍五入,取绝对值后舍入,然后加上符号,遇到.5的时候向绝对值小的方向舍之。

6.ImageView图片显示

//Drawable 显示SD卡里图片
Drawable drawable = Drawable
					.createFromPath(ConstantEp.path_reading01_images + path);
			System.out.println("drawable :"+drawable);
			ivPic.setImageDrawable(drawable);
//Bitmap 显示SD卡里图片
			Bitmap b = ImageCacheUtil.getResizedBitmap(null, null,   
			        mContext, ImageCacheUtil.readSdPic(ConstantEp.path_reading01_images + path), 80, false);  
			ivPic.setImageBitmap(b);

//反射 显示图片		
int id = BaseCommon.getImage(mContext, path.substring(0, path.length()-4));
			System.out.println("id :"+id);
			ivPic.setImageResource(id);

//ImageCacheUtil

import java.io.File;
import java.io.InputStream;

import android.content.ContentResolver;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.net.Uri;
import android.os.Environment;

/**
 * @author frankiewei. 工具类.
 */
public class ImageCacheUtil {

	/**
	 * 获取合适的Bitmap平时获取Bitmap就用这个方法吧.
	 * 
	 * @param path
	 *            路径.
	 * @param data
	 *            byte[]数组.
	 * @param context
	 *            上下文
	 * @param uri
	 *            uri
	 * @param target
	 *            模板宽或者高的大小.
	 * @param width
	 *            是否是宽度
	 * @return
	 */
	public static Bitmap getResizedBitmap(String path, byte[] data,
			Context context, Uri uri, int target, boolean width) {
		Options options = null;

		if (target > 0) {

			/*Options info = new Options();
			// 这里设置true的时候,decode时候Bitmap返回的为空,
			// 将图片宽高读取放在Options里.
			info.inJustDecodeBounds = false;
			info.inPreferredConfig = Bitmap.Config.RGB_565;
			
			decode(path, data, context, uri, info);

			int dim = info.outWidth;
			if (!width)
				dim = Math.max(dim, info.outHeight);
			int ssize = sampleSize(dim, target);*/
			int ssize = 1;
			options = new Options();
			options.inPreferredConfig=Bitmap.Config.RGB_565;//表示16位位图 565代表对应三原色占的位数
			options.inInputShareable=true;
			options.inPurgeable=true;//设置图片可以被回收
			options.inSampleSize = ssize;
		}
		Bitmap bm = null;
		try {
			bm = decode(path, data, context, uri, options);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return bm;

	}

	/**
	 * 解析Bitmap的公用方法.
	 * 
	 * @param path
	 * @param data
	 * @param context
	 * @param uri
	 * @param options
	 * @return
	 */
	public static Bitmap decode(String path, byte[] data, Context context,
			Uri uri, BitmapFactory.Options options) {

		Bitmap result = null;

		if (path != null) {
			result = BitmapFactory.decodeFile(path, options);
		} else if (data != null) {
			result = BitmapFactory.decodeByteArray(data, 0, data.length,
					options);
		} else if (uri != null) {
			// uri不为空的时候context也不要为空.
			ContentResolver cr = context.getContentResolver();
			InputStream inputStream = null;

			try {
				inputStream = cr.openInputStream(uri);
				result = BitmapFactory.decodeStream(inputStream, null, options);
				inputStream.close();
			} catch (Exception e) {
				e.printStackTrace();
			} catch (OutOfMemoryError e) {
				e.printStackTrace();
			}

		}

		return result;
	}

	/**
	 * 获取合适的sampleSize. 这里就简单实现都是2的倍数啦.
	 * 
	 * @param width
	 * @param target
	 * @return
	 */
	private static int sampleSize(int width, int target) {
		int result = 1;
		for (int i = 0; i < 10; i++) {
			if (width < target * 2) {
				break;
			}
			width = width / 2;
			result = result * 2;
		}
		return result;
	}
	
	
	/**
	 *  读取本地图片
	 * @param context
	 * @param id=等价=R.drawable.pic
	 * @return
	 */
	public Bitmap recodeResPic(Context context , int id, int target) {
		Resources r = context.getResources();
		Uri uri = Uri.parse(ContentResolver.SCHEME_ANDROID_RESOURCE
				+ "://" + r.getResourcePackageName(id)
				+ "/" + r.getResourceTypeName(id) + "/"
				+ r.getResourceEntryName(id));
		Bitmap bitmap = ImageCacheUtil.getResizedBitmap(null, null,
				context, uri, target, false);
//		Bitmap bitmap = ImageCacheUtil.getResizedBitmap(null, null,
//				context, uri, 400, false);
		return bitmap;
	}
	
	// 本地sd卡里的图片读取转换成URI
	public static Uri readSdPic(String path) {
		File file = new File(path);
		return Uri.fromFile(file);
	}
	
	public Bitmap recodeResPic(Context context , int id) {
		Resources r = context.getResources();
		Uri uri = Uri.parse(ContentResolver.SCHEME_ANDROID_RESOURCE
				+ "://" + r.getResourcePackageName(id)
				+ "/" + r.getResourceTypeName(id) + "/"
				+ r.getResourceEntryName(id));
		Bitmap bitmap = ImageCacheUtil.getResizedBitmap(null, null,
				context, uri, 100, false);
		return bitmap;
	}
	
}

7.ImageView

ImageViewandroid:scaleType="centerCrop"

CENTER:在视图中使图像居中,不执行缩放。

CENTER_CROP:均衡的缩放图像(保持图像原始比例),使图片的两个坐标(宽、高)都大于等于相应的视图坐标(负的内边距)

CENTER_INSIDE:均衡的缩放图像(保持图像原始比例),使图片的两个坐标(宽、高)都小于等于相应的视图坐标(负的内边距)

FIT_CENTER:使用CENTER方式缩放图像

FIT_END:使用END方式缩放图像

FIT_START:使用START方式缩放图像

FIT_XY:使用FILL方式缩放图像

MATRIX:绘制时,使用图像矩阵方式缩放

8.实现水平ListView,并且解决水平ListView在ScrollView中出现的滑动冲突

链接:http://liucanwen.iteye.com/blog/2020004

9.获得控件的宽高

// 获取控件的宽高
    private int getViewWidth(View view) {
        int w = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
        int h = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
        view.measure(w, h);
        int height = view.getMeasuredHeight();
        int width = view.getMeasuredWidth();
        System.out.println("measure width=" + width + " height=" + height);
        return width;
    }

显示本地图片报错:OOM

[size=medium]public Bitmap readBitmap(Context context, int id){
	     BitmapFactory.Options opt = new BitmapFactory.Options();
	     opt.inPreferredConfig=Bitmap.Config.RGB_565;//表示16位位图 565代表对应三原色占的位数
	     opt.inInputShareable=true;
	     opt.inPurgeable=true;//设置图片可以被回收
	     InputStream is = context.getResources().openRawResource(id);
	     return BitmapFactory.decodeStream(is, null, opt);
	}  
	
	private AnimationDrawable setData(Context context) {
		AnimationDrawable frameAnim = new AnimationDrawable();
		for (int i = 0; i <10; i++) {
			int resId = new BaseCommon().getImageId(context, ("star_" + i)); 
			Bitmap bmp = readBitmap(mContext, resId);
			BitmapDrawable bmpDraw = new BitmapDrawable(bmp);
			frameAnim.addFrame(bmpDraw, 200);
		}
		// 设置为循环播放
		frameAnim.setOneShot(true);
		// 设置ImageView的背景为AnimationDrawable
		return frameAnim;
	}[/size]

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