Question

我正在使用一个viewpager，它将从webservice获取图像源，并动态地将页面添加到viewpager。

但就目前而言，我只是在测试如何以编程方式更改图像。

这是简单的布局：

<?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>

这是来自ViewPager类的instantiateItem：

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;
        }

我在setImageDrawable上遇到异常，这里是stacktrace：

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)

任何人都知道我能尝试什么？我可以看到它是某种测量问题，但我不知道如何处理这个问题。

提前致谢

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

请尝试这种方式：

imageView1.setImageResource(R.drawable.button_increase);

Answer 3

试试这个

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

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

如何在viewpager中以编程方式更改图像？

3 个答案: