我们有时候在iPhone手机上或者Windows上面看到动态的图片,可以通过鼠标或者手指触摸来移动它,产生动态的图片滚动效果,还可以根据你的点击或者触摸触发其他事件响应。同样的,在Android中也提供这这种实现,这就是通过Gallery在UI上实现缩略图浏览器。
一般情况下,我们在Android中要用到类似这种图片容器的控件,都需要为它指定一个适配器,让它可以把内容按照我们定义的方式来显示,因此我们来给它加一个适配器,至于这个适配器如何实现,后面接着来操作,这里只需知道这个适配器的类叫ImageGalleryAdapter 。 gallery.setAdapter(new ImageGalleryAdapter (this));
下面介绍常用2种用法:
第一种方法:
第一步:设计xml布局文件
代码如下:main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <Gallery android:id="@+id/myGallery" android:layout_width="fill_parent" android:layout_height="wrap_content" android:gravity="center_vertical" android:spacing="3px" android:text="@string/hello" /> </LinearLayout>
package net.loonggg.gallery; import android.content.Context; import android.view.View; import android.view.ViewGroup; import android.view.ViewGroup.LayoutParams; import android.widget.BaseAdapter; import android.widget.Gallery; import android.widget.ImageView; public class ImageGalleryAdapter extends BaseAdapter { private Context context; // 里面所有的方法表示的是可以根据指定的显示图片的数量,进行每个图片的处理 private int[] image = new int[] { R.drawable.ispic_a, R.drawable.ispic_b, R.drawable.ispic_c, R.drawable.ispic_d, R.drawable.ispic_e }; public ImageGalleryAdapter(Context context) { this.context = context; } public int getCount() { // 取得要显示内容的数量 return image.length; } public Object getItem(int position) { // 每个资源的位置 return image[position]; } public long getItemId(int position) { // 取得每个项的ID return image[position]; } // 将资源设置到一个组件之中,很明显这个组件是ImageView public View getView(int position, View convertView, ViewGroup parent) { ImageView iv = new ImageView(context); iv.setBackgroundColor(0xFFFFFFFF); iv.setImageResource(image[position]);// 给ImageView设置资源 iv.setScaleType(ImageView.ScaleType.CENTER);// 设置对齐方式 iv.setLayoutParams(new Gallery.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT)); return iv; } }第三步:主方法:
package net.loonggg.gallery; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.AdapterView; import android.widget.AdapterView.OnItemClickListener; import android.widget.Gallery; import android.widget.Toast; public class GalleryActivity extends Activity { private Gallery myGallery; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); myGallery = (Gallery) findViewById(R.id.myGallery); myGallery.setAdapter(new ImageGalleryAdapter(this)); myGallery.setOnItemClickListener(new OnItemClickListenerImpl()); } private class OnItemClickListenerImpl implements OnItemClickListener { public void onItemClick(AdapterView<?> parent, View view, int position, long id) { Toast.makeText(GalleryActivity.this, String.valueOf(position), Toast.LENGTH_SHORT).show(); } } }
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:gravity="bottom" android:orientation="vertical" > <ImageSwitcher android:id="@+id/is" android:layout_width="fill_parent" android:layout_height="wrap_content" > </ImageSwitcher> <Gallery android:id="@+id/myGallery" android:layout_width="fill_parent" android:layout_height="wrap_content" android:gravity="center_vertical" android:spacing="3px" /> </LinearLayout>
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="wrap_content" android:layout_height="wrap_content" android:background="#FFFFFF" android:orientation="horizontal" > <ImageView android:id="@+id/iv" android:layout_width="wrap_content" android:layout_height="wrap_content" android:scaleType="center" /> </LinearLayout>
package net.loonggg.gallery2; import java.lang.reflect.Field; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.ViewGroup.LayoutParams; import android.widget.AdapterView; import android.widget.AdapterView.OnItemClickListener; import android.widget.Gallery; import android.widget.ImageSwitcher; import android.widget.ImageView; import android.widget.SimpleAdapter; import android.widget.ViewSwitcher.ViewFactory; public class MainActivity extends Activity { private ImageSwitcher is; private Gallery gallery; private SimpleAdapter adapter; private List<Map<String, Integer>> list = new ArrayList<Map<String, Integer>>(); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); is = (ImageSwitcher) findViewById(R.id.is); is.setFactory(new ViewFactoryImpl()); initAdapter(); gallery = (Gallery) findViewById(R.id.myGallery); gallery.setAdapter(adapter); // 为gallery设置合适的适配器 gallery.setOnItemClickListener(new OnItemClickListenerImpl()); } public class OnItemClickListenerImpl implements OnItemClickListener { // gallery的点击事件 @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { Map<String, Integer> map = (Map<String, Integer>) parent .getAdapter().getItem(position); is.setImageResource(map.get("image")); } } public void initAdapter() { // 这个方法的功能是:从R.java文件中获取图片资源的id,如果资源图片数量比较多,用数组的方法一一定义,就不太合适,这种方法最好了。 Field[] fields = R.drawable.class.getDeclaredFields(); for (int x = 0; x < fields.length; x++) { if (fields[x].getName().startsWith("ispic_")) { // 根据图片的名称取出想要的图片 Map<String, Integer> map = new HashMap<String, Integer>(); try { map.put("image", fields[x].getInt(R.drawable.class)); } catch (Exception e) { e.printStackTrace(); } list.add(map); } } adapter = new SimpleAdapter(MainActivity.this, list, R.layout.grid_item, new String[] { "image" }, new int[] { R.id.iv }); } public class ViewFactoryImpl implements ViewFactory { @Override public View makeView() { ImageView iv = new ImageView(MainActivity.this); iv.setBackgroundColor(0xFFFFFFFF); iv.setScaleType(ImageView.ScaleType.CENTER); iv.setLayoutParams(new ImageSwitcher.LayoutParams( LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT)); return iv; } } }
这个基本思路是:
1,创建一个源图一样的图,利用martrix将图片旋转180度。这个倒影图的高是源图的一半。
Matrix matrix = new Matrix(); // 1表示放大比例,不放大也不缩小。 // -1表示在y轴上相反,即旋转180度。 matrix.preScale(1, -1); Bitmap reflectionBitmap = Bitmap.createBitmap( srcBitmap, 0, srcBitmap.getHeight() / 2, // top为源图的一半 srcBitmap.getWidth(), // 宽度与源图一样 srcBitmap.getHeight() / 2, // 高度与源图的一半 matrix, false);2,创建一个最终效果的图,即源图 + 间隙 + 倒影。
final int REFLECTION_GAP = 5; Bitmap bitmapWithReflection = Bitmap.createBitmap( reflectionWidth, srcHeight + reflectionHeight + REFLECTION_GAP, Config.ARGB_8888);
Canvas canvas = new Canvas(bitmapWithReflection); // Draw the original bitmap. canvas.drawBitmap(srcBitmap, 0, 0, null); // Draw the reflection bitmap. canvas.drawBitmap(reflectionBitmap, 0, srcHeight + REFLECTION_GAP, null);4,创建LinearGradient,从而给定一个由上到下的渐变色。
Paint paint = new Paint(); paint.setAntiAlias(true); LinearGradient shader = new LinearGradient( 0, srcHeight, 0, bitmapWithReflection.getHeight() + REFLECTION_GAP, 0x70FFFFFF, 0x00FFFFFF, TileMode.MIRROR); paint.setShader(shader); paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.DST_IN)); // Draw the linear shader. canvas.drawRect( 0, srcHeight, srcWidth, bitmapWithReflection.getHeight() + REFLECTION_GAP, paint);
扩展系统的gallery,我们需要重写两个方法,getChildStaticTransformation()和getChildDrawingOrder(),同时,要使这两个方法能被调用,必须执行如下两行代码,文档上面是有说明的。
// Enable set transformation. this.setStaticTransformationsEnabled(true); // Enable set the children drawing order. this.setChildrenDrawingOrderEnabled(true);
@Override protected int getChildDrawingOrder(int childCount, int i) { // Current selected index. int selectedIndex = getSelectedItemPosition() - getFirstVisiblePosition(); if (selectedIndex < 0) { return i; } if (i < selectedIndex) { return i; } else if (i >= selectedIndex) { return childCount - 1 - i + selectedIndex; } else { return i; } }
这里为什么要计算drawing order,因为从上图中看到,我们的效果是:中间左边的顺序是 0, 1, 2,右边的child覆盖左边的child,而在中间右边的顺序正好相反,左边的覆盖右边的,所以我们要重写这个方法,而gallery自身的实现,不是这种效果。
@Override protected boolean getChildStaticTransformation(View child, Transformation t) { super.getChildStaticTransformation(child, t); final int childCenter = getCenterOfView(child); final int childWidth = child.getWidth(); int rotationAngle = 0; t.clear(); t.setTransformationType(Transformation.TYPE_MATRIX); // If the child is in the center, we do not rotate it. if (childCenter == mCoveflowCenter) { transformImageBitmap(child, t, 0); } else { // Calculate the rotation angle. rotationAngle = (int)(((float)(mCoveflowCenter - childCenter) / childWidth) * mMaxRotationAngle); // Make the angle is not bigger than maximum. if (Math.abs(rotationAngle) > mMaxRotationAngle) { rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle : mMaxRotationAngle; } transformImageBitmap(child, t, rotationAngle); } return true; }
这个方法就是根据child来计算它的transformation(变换),我们需要去修改它里面的matrix,从而达到旋转的效果。根据位置和角度来计算的matrix的方法写在另外一个方法transformImageBitmap中实现。
private void transformImageBitmap(View child, Transformation t, int rotationAngle) { mCamera.save(); final Matrix imageMatrix = t.getMatrix(); final int imageHeight = child.getHeight(); final int imageWidth = child.getWidth(); final int rotation = Math.abs(rotationAngle); // Zoom on Z axis. mCamera.translate(0, 0, mMaxZoom); if (rotation < mMaxRotationAngle) { float zoomAmount = (float)(mMaxZoom + rotation * 1.5f); mCamera.translate(0, 0, zoomAmount); } // Rotate the camera on Y axis. mCamera.rotateY(rotationAngle); // Get the matrix from the camera, in fact, the matrix is S (scale) transformation. mCamera.getMatrix(imageMatrix); // The matrix final is T2 * S * T1, first translate the center point to (0, 0), // then scale, and then translate the center point to its original point. // T * S * T // S * T1 imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2)); // (T2 * S) * T1 imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2)); mCamera.restore(); }
第一,先在Z轴上平称,其实就是得到一个缩放矩阵变换,我这里简写为 S。
第二,是利用camera这个类来生成matrix,其实mCamera.rotateY就是围绕Y轴旋转。这里生成了一个旋转矩阵,记为 R 。经过这两步,此时调用mCamera.getMatrix(imageMatrix); 从Camera中得到matrix,此时这个矩阵中包含了S * R。
第三,最关键是下面两句
// S * T1 imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2)); // (T2 * S) * T1 imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2));
M = T * (S * R) * T1 (这里在T1表示与T相反)。
GalleryFlow.java
import android.content.Context; import android.graphics.Camera; import android.graphics.Matrix; import android.util.AttributeSet; import android.view.View; import android.view.animation.Transformation; import android.widget.Gallery; public class GalleryFlow extends Gallery { /** * The camera class is used to 3D transformation matrix. */ private Camera mCamera = new Camera(); /** * The max rotation angle. */ private int mMaxRotationAngle = 60; /** * The max zoom value (Z axis). */ private int mMaxZoom = -120; /** * The center of the gallery. */ private int mCoveflowCenter = 0; public GalleryFlow(Context context) { this(context, null); } public GalleryFlow(Context context, AttributeSet attrs) { this(context, attrs, 0); } public GalleryFlow(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); // Enable set transformation. this.setStaticTransformationsEnabled(true); // Enable set the children drawing order. this.setChildrenDrawingOrderEnabled(true); } public int getMaxRotationAngle() { return mMaxRotationAngle; } public void setMaxRotationAngle(int maxRotationAngle) { mMaxRotationAngle = maxRotationAngle; } public int getMaxZoom() { return mMaxZoom; } public void setMaxZoom(int maxZoom) { mMaxZoom = maxZoom; } @Override protected int getChildDrawingOrder(int childCount, int i) { // Current selected index. int selectedIndex = getSelectedItemPosition() - getFirstVisiblePosition(); if (selectedIndex < 0) { return i; } if (i < selectedIndex) { return i; } else if (i >= selectedIndex) { return childCount - 1 - i + selectedIndex; } else { return i; } } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { mCoveflowCenter = getCenterOfCoverflow(); super.onSizeChanged(w, h, oldw, oldh); } private int getCenterOfView(View view) { return view.getLeft() + view.getWidth() / 2; } @Override protected boolean getChildStaticTransformation(View child, Transformation t) { super.getChildStaticTransformation(child, t); final int childCenter = getCenterOfView(child); final int childWidth = child.getWidth(); int rotationAngle = 0; t.clear(); t.setTransformationType(Transformation.TYPE_MATRIX); // If the child is in the center, we do not rotate it. if (childCenter == mCoveflowCenter) { transformImageBitmap(child, t, 0); } else { // Calculate the rotation angle. rotationAngle = (int)(((float)(mCoveflowCenter - childCenter) / childWidth) * mMaxRotationAngle); // Make the angle is not bigger than maximum. if (Math.abs(rotationAngle) > mMaxRotationAngle) { rotationAngle = (rotationAngle < 0) ? -mMaxRotationAngle : mMaxRotationAngle; } transformImageBitmap(child, t, rotationAngle); } return true; } private int getCenterOfCoverflow() { return (getWidth() - getPaddingLeft() - getPaddingRight()) / 2 + getPaddingLeft(); } private void transformImageBitmap(View child, Transformation t, int rotationAngle) { mCamera.save(); final Matrix imageMatrix = t.getMatrix(); final int imageHeight = child.getHeight(); final int imageWidth = child.getWidth(); final int rotation = Math.abs(rotationAngle); // Zoom on Z axis. mCamera.translate(0, 0, mMaxZoom); if (rotation < mMaxRotationAngle) { float zoomAmount = (float)(mMaxZoom + rotation * 1.5f); mCamera.translate(0, 0, zoomAmount); } // Rotate the camera on Y axis. mCamera.rotateY(rotationAngle); // Get the matrix from the camera, in fact, the matrix is S (scale) transformation. mCamera.getMatrix(imageMatrix); // The matrix final is T2 * S * T1, first translate the center point to (0, 0), // then scale, and then translate the center point to its original point. // T * S * T // S * T1 imageMatrix.postTranslate((imageWidth / 2), (imageHeight / 2)); // (T2 * S) * T1 imageMatrix.preTranslate(-(imageWidth / 2), -(imageHeight / 2)); mCamera.restore(); } }BitmapUtil.java
package com.lee.gallery3d.utils; import android.graphics.Bitmap; import android.graphics.Bitmap.Config; import android.graphics.Canvas; import android.graphics.LinearGradient; import android.graphics.Matrix; import android.graphics.Paint; import android.graphics.PixelFormat; import android.graphics.PorterDuffXfermode; import android.graphics.Shader.TileMode; import android.graphics.drawable.Drawable; public class BitmapUtil { public static Bitmap createReflectedBitmap(Bitmap srcBitmap) { if (null == srcBitmap) { return null; } // The gap between the reflection bitmap and original bitmap. final int REFLECTION_GAP = 4; int srcWidth = srcBitmap.getWidth(); int srcHeight = srcBitmap.getHeight(); int reflectionWidth = srcBitmap.getWidth(); int reflectionHeight = srcBitmap.getHeight() / 2; if (0 == srcWidth || srcHeight == 0) { return null; } // The matrix Matrix matrix = new Matrix(); matrix.preScale(1, -1); try { // The reflection bitmap, width is same with original's, height is half of original's. Bitmap reflectionBitmap = Bitmap.createBitmap( srcBitmap, 0, srcHeight / 2, srcWidth, srcHeight / 2, matrix, false); if (null == reflectionBitmap) { return null; } // Create the bitmap which contains original and reflection bitmap. Bitmap bitmapWithReflection = Bitmap.createBitmap( reflectionWidth, srcHeight + reflectionHeight + REFLECTION_GAP, Config.ARGB_8888); if (null == bitmapWithReflection) { return null; } // Prepare the canvas to draw stuff. Canvas canvas = new Canvas(bitmapWithReflection); // Draw the original bitmap. canvas.drawBitmap(srcBitmap, 0, 0, null); // Draw the reflection bitmap. canvas.drawBitmap(reflectionBitmap, 0, srcHeight + REFLECTION_GAP, null); Paint paint = new Paint(); paint.setAntiAlias(true); LinearGradient shader = new LinearGradient( 0, srcHeight, 0, bitmapWithReflection.getHeight() + REFLECTION_GAP, 0x70FFFFFF, 0x00FFFFFF, TileMode.MIRROR); paint.setShader(shader); paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.DST_IN)); // Draw the linear shader. canvas.drawRect( 0, srcHeight, srcWidth, bitmapWithReflection.getHeight() + REFLECTION_GAP, paint); return bitmapWithReflection; } catch (Exception e) { e.printStackTrace(); } return null; } }