如何在viewpager中以編程方式更改圖像？

Question

我使用的是viewpager，將獲得的圖像源從一個Web服務，並動態頁面添加到viewpager。

但現在，我只是測試如何編程改變形象。

這是簡單的佈局：

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical" > 

    <ImageView 
     android:id="@+id/imageView1" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:scaleType="centerInside" 
     android:src="@drawable/button_increase" /> 

</LinearLayout> 

這裏的instantiateItem從ViewPager類：

public Object instantiateItem(View collection, int position) { 

      LayoutInflater inflater = (LayoutInflater) collection.getContext() 
        .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 

      View view = inflater.inflate(R.layout.test_layout, null); 

      ImageView imageView1= ((ImageView)(View)findViewById(R.id.imageView1)); 
      imageView1.setImageDrawable(getResources().getDrawable(R.drawable.button_increase)); 

      ((ViewPager) collection).addView(view); 

      return view; 
     } 

我得到setImageDrawable異常，這裏的堆棧跟蹤：

06-05 14:58:17.923: E/AndroidRuntime(22982): FATAL EXCEPTION: main 
06-05 14:58:17.923: E/AndroidRuntime(22982): java.lang.NullPointerException 
06-05 14:58:17.923: E/AndroidRuntime(22982): at *project*.MainActivity$CustomPagerAdapter.instantiateItem(MainActivity.java:93) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.support.v4.view.PagerAdapter.instantiateItem(PagerAdapter.java:110) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:649) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.support.v4.view.ViewPager.populate(ViewPager.java:783) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1016) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.view.View.measure(View.java:12863) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:594) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:376) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.view.View.measure(View.java:12863) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.view.View.measure(View.java:12863) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.widget.LinearLayout.measureVertical(LinearLayout.java:812) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.view.View.measure(View.java:12863) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2256) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.view.View.measure(View.java:12863) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1197) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2585) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.os.Handler.dispatchMessage(Handler.java:99) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.os.Looper.loop(Looper.java:137) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at android.app.ActivityThread.main(ActivityThread.java:4507) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at java.lang.reflect.Method.invokeNative(Native Method) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at java.lang.reflect.Method.invoke(Method.java:511) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557) 
06-05 14:58:17.923: E/AndroidRuntime(22982): at dalvik.system.NativeStart.main(Native Method) 

任何人都知道我可以嘗試什麼？ 我可以看到它是某種度量問題，但我不知道在這個問題上該怎麼做。

在此先感謝

Answer 1

而不是

ImageView imageView1= ((ImageView)(View)findViewById(R.id.imageView1)); 

使用

ImageView imageView1= ((ImageView) view.findViewById(R.id.imageView1)); 

Answer 2

嘗試這種方式來代替：

imageView1.setImageResource(R.drawable.button_increase); 

Answer 3

試試這個

View view = inflater.inflate(R.layout.test_layout, null); 

     ImageView imageView1= (ImageView)view.findViewById(R.id.imageView1); 
     imageView1.setImageResource(R.drawable.button_increase);