Drawable与Bitmap 自定义
Drawable简介
Drawable是Android平下通用的图形对象,它可以装载常用格式的图像,比如GIF、PNG、JPG,当然也支持BMP。相比于View,我们并不需要去考虑如何measure、layout,仅仅只要去考虑如何draw(canavs)。Though usually not visible to the application, Drawables may take a variety of forms 形式: Bitmap: the simplest Drawable, a PNG or JPEG image. Nine Patch: an extension 引申、扩展 to the PNG format allows it to specify 描述 information about how to stretch 延伸、拉长 it and place things inside of it. Shape: contains simple drawing commands 命令 instead of a raw 原始 bitmap, allowing it to resize 调整大小 better in some cases. Layers: a compound 合成的 drawable, which draws multiple 多重的、复杂的 underlying 底层的 drawables on top of each other. States: a compound drawable that selects one of a set of drawables based on its state. Levels: a compound drawable that selects one of a set of drawables based on its level. Scale: a compound drawable with a single 单一的 child drawable, whose overall 全部的 size is modified 可改变的 based on the current level.Drawable在xml中的标签及其对应的实体类如下:
Drawable和Bitmap的区别
A bitmap is a Drawable. A Drawable is not necessarily 不一定是 a bitmap. Like all thumbs 拇指 are fingers 手指 but not all fingers are thumbs.Bitmap,代表一个位图图像,Android支持三种格式的位图图像:.png (preferred 图片优先),.jpg (acceptable 也可以 但是效果没有.png好), .gif (discouraged 支持最差),当然编码器也有很多,如RGB565、RGB888。作为一种逐像素的显示方式,其执行效率高,但是缺点也很明显,存储效率低。另外要注意,在构建应用的时候,Bitmap文件可能会被appt工具压缩自动优化为无损图像。例如,一个真彩色PNG,不需要超过256的颜色可以被转换成一个8位PNG和调色板。这将导致一个图像质量相同,但这需要更少的内存。所以要意识到,在drawable目录中图像的二进制文件在构建程序时可能被改变。如果你打算读一个图像作为字节流并将它转换成一个位图,把你的图片放在在res /raw/文件夹里,在那里他们不会被优化。
两者对比:对比项 显示清晰度 占用内存 支持缩放 支持色相色差调整 支持旋转 支持透明色 绘制速度 支持像素操作Bitmap 相同 大 是 是 是 是 慢 是Drawable 相同 小 是 否 是 是 快 否Drawable在内存占用和绘制速度这两个非常关键的点上胜过Bitmap,但是不支持色相色差调整,不支持像素操作。
设置Drawable时的注意事项
在代码中设置Drawable有两种方式Drawable drawable = getResources().getDrawable(R.drawable.ic_launcher);rb.setCompoundDrawablesWithIntrinsicBounds(null, drawable, null, null);drawable.setBounds(0, 0, mDrawable.getIntrinsicWidth(), mDrawable.getIntrinsicHeight());rb.setCompoundDrawables(null, drawable, null, null);1、setCompoundDrawables方法Sets the Drawables (if any) to appear to the left of, above, to the right of, and below the text. Use null if you do not want a Drawable there. The Drawables must already have had setBounds(Rect) called.这个方法要先给Drawable设置drawable.setBounds(left, top, right, bottom),即组件在容器X、Y轴上的起点(相对自身),长度、高度。如:drawable.setBounds(0, 0, mDrawable.getIntrinsicWidth(), mDrawable.getIntrinsicHeight());若没设置,则setCompoundDrawables后不会显示图片!好处是可以打破原有的大小及比例自由设置图片大小。2、setCompoundDrawablesWithIntrinsicBounds()方法Sets the Drawables (if any) to appear to the left of, above, to the right of, and below the text. Use null if you do not want a Drawable there. The Drawables' bounds will be set to their intrinsic bounds.可以在上、下、左、右设置图标,如果不想在某个地方显示,则设置为null。图标的宽高将会设置为固有宽高。不过只能在高版本中才能使用此方法。
自定义圆形Drawabe
public class CircleImageDrawable extends Drawable {private Paint mPaint;private int mWidth;private Bitmap mBitmap;public CircleImageDrawable(Bitmap bitmap) {mBitmap = bitmap;mPaint = new Paint();mPaint.setAntiAlias(true);//BitmapShader通过设置给mPaint,然后用这个mPaint绘图时,就会根据你设置的TileMode,对绘制区域进行着色mPaint.setShader(new BitmapShader(bitmap, TileMode.CLAMP, TileMode.CLAMP));mWidth = Math.min(mBitmap.getWidth(), mBitmap.getHeight());}@Overridepublic void draw(Canvas canvas) {//必须重写的方法canvas.drawCircle(mWidth / 2, mWidth / 2, mWidth / 2, mPaint);}@Overridepublic void setAlpha(int alpha) {//必须重写的方法mPaint.setAlpha(alpha);}@Overridepublic void setColorFilter(ColorFilter cf) {//必须重写的方法mPaint.setColorFilter(cf);}@Overridepublic int getOpacity() {//必须重写的方法return PixelFormat.TRANSLUCENT;}@Overridepublic int getIntrinsicWidth() {//在View使用wrap_content的时候,提供Drawable的尺寸return mWidth;}@Overridepublic int getIntrinsicHeight() {return mWidth;}}public class CircleImageDrawableActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.icon);((ImageView) findViewById(R.id.id_one)).setImageDrawable(new CircleImageDrawable(bitmap));//wrap_content((ImageView) findViewById(R.id.id_two)).setImageDrawable(new CircleImageDrawable(bitmap));//120dp}}
自定义圆角矩形Drawabe
public class RoundImageDrawable extends Drawable {private Paint mPaint;private Bitmap mBitmap;private RectF rectF;private float rx, ry;public RoundImageDrawable(Bitmap bitmap, float rx, float ry) {mBitmap = bitmap;this.rx = rx;this.ry = ry;mPaint = new Paint();mPaint.setAntiAlias(true);mPaint.setShader(new BitmapShader(bitmap, TileMode.CLAMP, TileMode.CLAMP));}@Overridepublic void setBounds(int left, int top, int right, int bottom) {//设置绘制的范围super.setBounds(left, top, right, bottom);rectF = new RectF(left, top, right, bottom);}@Overridepublic void draw(Canvas canvas) {canvas.drawRoundRect(rectF, rx, ry, mPaint);}@Overridepublic int getIntrinsicWidth() {return mBitmap.getWidth();}@Overridepublic int getIntrinsicHeight() {return mBitmap.getHeight();}@Overridepublic void setAlpha(int alpha) {mPaint.setAlpha(alpha);}@Overridepublic void setColorFilter(ColorFilter cf) {mPaint.setColorFilter(cf);}@Overridepublic int getOpacity() {return PixelFormat.TRANSLUCENT;}}public class RoundImageDrawableActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.icon);((ImageView) findViewById(R.id.id_one)).setImageDrawable(new RoundImageDrawable(bitmap, 60, 60));((ImageView) findViewById(R.id.id_two)).setImageDrawable(new RoundImageDrawable(bitmap, 30, 30));}}
自定义Drawable的状态
1、自定义属性<?xml version="1.0" encoding="utf-8"?><resources><declare-styleable name="MessageStatus"><attr name="state_message_readed" format="boolean" /></declare-styleable></resources>2、自定义Viewpublic class MessageListItem extends RelativeLayout {private static final int[] STATE_MESSAGE_READED = { R.attr.state_message_readed };private boolean mMessgeReaded = false;public MessageListItem(Context context, AttributeSet attrs) {super(context, attrs);}public void setMessageReaded(boolean readed) {if (this.mMessgeReaded != readed) {mMessgeReaded = readed;refreshDrawableState();}}@Overrideprotected int[] onCreateDrawableState(int extraSpace) {//在mMessgeReaded=true的情况下,把我们自定义的状态添加进去if (mMessgeReaded) {int[] drawableState = super.onCreateDrawableState(extraSpace + 1);mergeDrawableStates(drawableState, STATE_MESSAGE_READED);return drawableState;}return super.onCreateDrawableState(extraSpace);}}3、布局中使用自定义View<com.bqt.drawable.view.MessageListItem xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="50dp"android:background="@drawable/message_item_bg" ><ImageViewandroid:id="@+id/icon"android:layout_width="30dp"android:layout_height="wrap_content"android:layout_alignParentLeft="true"android:layout_centerVertical="true"android:duplicateParentState="true"android:src="@drawable/message_item_icon_bg" /><TextViewandroid:id="@+id/text"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_centerVertical="true"android:layout_toRightOf="@id/icon" /></com.bqt.drawable.view.MessageListItem>4、代码中设置此View的状态public class CustomStateDrawableActivity extends ListActivity {private MessageBean[] messages = new MessageBean[10];@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);for (int i = 0; i < messages.length; i++) {messages[i] = new MessageBean(i + "", true & (i == 1 || i == 5 || i == 6 || i == 8));}getListView().setAdapter(new ArrayAdapter<MessageBean>(this, -1, messages) {@Overridepublic View getView(int position, View convertView, ViewGroup parent) {if (convertView == null) {convertView = LayoutInflater.from(CustomStateDrawableActivity.this).inflate(R.layout.item_msg_list, parent, false);}((TextView) convertView.findViewById(R.id.text)).setText(getItem(position).message);((MessageListItem) convertView).setMessageReaded(getItem(position).readed);return convertView;}});}}
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