java - 如何以编程方式将 View 添加到 ViewContainer？

Question

当我重写 MainAdapter extends PagerAdapter 的 public Object instantiateItem 函数时，在 container.addView( 行，它崩溃了。我收到以下日志

java.lang.IllegalArgumentException: Cannot add a null child view to a ViewGroup
        at android.view.ViewGroup.addViewInLayout(ViewGroup.java:3909)
        at android.view.ViewGroup.addViewInLayout(ViewGroup.java:3890)
        at android.support.v4.view.ViewPager.addView(ViewPager.java:1302)
        at android.view.ViewGroup.addView(ViewGroup.java:3744)
        at com.jfeinstein.jazzyviewpager.JazzyViewPager.addView(JazzyViewPager.java:127)
        at com.ycg.bottommenuslidegradientswipe.MainActivity$MainAdapter.instantiateItem(MainActivity.java:260)

我的instantiateItem函数的代码如下所示。类 TaskCompletedView 扩展 View

@Override
public Object instantiateItem(ViewGroup container, final int position) {
    TasksCompletedView mTasksView = (TasksCompletedView) findViewById(R.id.tasks_view);
    container.addView(mTasksView, LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT);
    jazzyPager.setObjectForPosition(mTasksView,position);

    new Thread(new ProgressRunable()).start();
    return mTasksView;
    }

Answer 1

发生这种情况是因为您设置了空变量。 mTasksView == null; 您需要放置非空 View ，例如:

container.addView(new ImageView(context), LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT);