Android当中切换图片

我们在Windows 平台上要查看很多张图片，最简单的方法就是通过Windows图片和传真查看器，在上一张和下一张之间切换，Android平台上可以通过ImageSwicher类来实现这一效果（事实上通过其他方法也是可以实现的Bitmap）ImageSwitcher类必须设置一个ViewFactory，主要用来将显示的图片和父窗口区分开，通过makeView()方法来显示图片，这里会返回一个ImageView对象，而方法setImageResource用来显示指定的图片资源。我们现在看一个实例，当点击上一张或者下一张图片的时候切换浏览另一张图片。这里首先通过自己在界面中实现LinearLayout的方式来实现：

void android.widget.ImageSwitcher.setImageResource(int resid)
 

public void setImageResource(int resid)Added inAPI level 1

 

 android.widget.LinearLayout.LayoutParams.LayoutParams(int width, int height)

 

public LinearLayout.LayoutParams(int width, int height)       Added inAPI level 1

android.widget.Button.Button(Context context)

public Button (Context context)Added inAPI level 1

void android.widget.ViewSwitcher.setFactory(ViewFactory factory)

public void setFactory(ViewSwitcher.ViewFactory factory)

Added in API level 1

Sets the factory used to create the two views between which the ViewSwitcher will flip. Instead of using a factory, you can calladdView(android.view.View, int, android.view.ViewGroup.LayoutParams) twice.

Parameters

factorythe view factory used to generate the switcher's content

void android.view.ViewGroup.addView(View child,LayoutParams params)

public void addView(View child,ViewGroup.LayoutParams params)

Added in API level 1

Adds a child view with the specified layout parameters.

Note: do not invoke this method from draw(android.graphics.Canvas),onDraw(android.graphics.Canvas),dispatchDraw(android.graphics.Canvas) or any related method.

Parameters

childthe child view to addparamsthe layout parameters to set on the child  

package com.example.activity01;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.ImageSwitcher;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.ViewSwitcher.ViewFactory;public class Activity01 extends Activity implements OnClickListener,ViewFactory{/* 所有要显示的图片资源索引 */private static final Integer[] imagelist = { R.drawable.img1, R.drawable.img2, R.drawable.img3,R.drawable.img4, R.drawable.img5, R.drawable.img6, R.drawable.img7, R.drawable.img8,     }; //创建ImageSwitcher对象private ImageSwitcherm_Switcher;//索引private  intindex= 0;//“下一页”按钮IDprivate static final intBUTTON_DWON_ID= 0x123456;//“上一页”按钮IDprivate static final intBUTTON_UP_ID= 0x123457;//ImageSwitcher对象的IDprivate static final intSWITCHER_ID= 0x123458;/** Called when the activity is first created. */@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);//创建一个线性布局LinearLayoutLinearLayout main_view = new LinearLayout(this);//创建ImageSwitcher对象m_Switcher = new ImageSwitcher(this);//在线性布局中添加ImageSwitcher视图main_view.addView(m_Switcher);//设置ImageSwitcher对象的IDm_Switcher.setId(SWITCHER_ID);//设置ImageSwitcher对象的数据源  首先放置图片  然后放置按钮m_Switcher.setFactory(this);m_Switcher.setImageResource(imagelist[index]);//设置显示上面创建的线性布局setContentView(main_view);//创建“下一张”按钮Button next = new Button(this);next.setId(BUTTON_DWON_ID);next.setText("下一张");next.setOnClickListener(this);//就是一个构造函数  用于生成LinearLayout.LayoutParams对象LinearLayout.LayoutParams param = new LinearLayout.LayoutParams(100, 100);main_view.addView(next, param);//创建“上一张”按钮Button pre = new Button(this);pre.setId(BUTTON_UP_ID);pre.setText("上一张");pre.setOnClickListener(this);main_view.addView(pre, param);}//事件监听、处理public void onClick(View v){switch (v.getId()){//下一页case BUTTON_DWON_ID:index++;if (index >= imagelist.length){index = 0;}//ImageSwitcher对象资源索引m_Switcher.setImageResource(imagelist[index]);break;//上一页case BUTTON_UP_ID:index--;if (index < 0){index = imagelist.length - 1;}//ImageSwitcher对象资源索引m_Switcher.setImageResource(imagelist[index]);break;default:break;}}public View makeView(){//将所有图片通过ImageView来显示return new ImageView(this);}}

下面是通过布局文件来设置界面组件的方式来实现的相关操作

<?xml version="1.0" encoding="utf-8"?>   <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"               android:orientation="vertical"               android:layout_width="fill_parent"               android:layout_height="fill_parent">       <LinearLayout                    android:orientation="horizontal"                     android:layout_width="fill_parent"                     android:layout_height="fill_parent"                     android:gravity="center"                    android:background="#f0f0f0"              >           <Button                   android:id="@+id/pre"                   android:layout_width="wrap_content"                   android:layout_height="wrap_content"                  android:layout_gravity="center"                android:text="@+string/pre"                  />           <ImageSwitcher                   android:id="@+id/switcher"                   android:layout_width="wrap_content"                   android:layout_height="wrap_content"                   android:layout_marginLeft="20dp"                  android:layout_marginRight="20dp"                  />           <Button                   android:id="@+id/next"                   android:layout_width="wrap_content"                   android:layout_height="wrap_content"                   android:layout_gravity="center"                  android:text="@+string/next"                />          </LinearLayout>   </ScrollView>   

package com.example.activity01;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.ImageSwitcher;import android.widget.ImageView;import android.widget.ViewSwitcher.ViewFactory;public class Activity01 extends Activity  implements ViewFactory{/* 所有要显示的图片资源索引 */private static final Integer[] imagelist = { R.drawable.img1, R.drawable.img2, R.drawable.img3,R.drawable.img4, R.drawable.img5, R.drawable.img6, R.drawable.img7, R.drawable.img8,     }; //创建ImageSwitcher对象private ImageSwitcher   m_Switcher = null;private Button   buttonNext = null;private Button   buttonPre = null;//索引private  int   index  = 0;/** Called when the activity is first created. */@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);buttonNext = (Button)findViewById(R.id.next);buttonPre  =(Button)findViewById(R.id.pre);m_Switcher = (ImageSwitcher)findViewById(R.id.switcher);m_Switcher.setFactory(this);m_Switcher.setImageResource(imagelist[index]);buttonNext.setOnClickListener(listener);buttonPre.setOnClickListener(listener);}//事件监听、处理OnClickListener listener = new OnClickListener(){public void onClick(View v){switch (v.getId()){//下一页case R.id.next:index++;if (index >= imagelist.length){index = 0;}//ImageSwitcher对象资源索引m_Switcher.setImageResource(imagelist[index]);break;//上一页case R.id.pre:index--;if (index < 0){index = imagelist.length - 1;}//ImageSwitcher对象资源索引m_Switcher.setImageResource(imagelist[index]);break;default:break;}}};@Overridepublic View makeView() {//将所有图片通过ImageView来显示return new ImageView(this);}}

很奇怪的一开始的界面布局xml文件并没有起作用