Android 使用 LinearLayout.LayoutParams 时出现 ClassCastException
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ClassCastException when using LinearLayout.LayoutParams
提问by tolgap
This is the exception:
这是例外：
07-20 19:52:14.193: E/AndroidRuntime(3908): FATAL EXCEPTION: main
07-20 19:52:14.193: E/AndroidRuntime(3908): java.lang.ClassCastException: android.view.ViewGroup$LayoutParams cannot be cast to android.widget.LinearLayout$LayoutParams
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.widget.LinearLayout.measureVertical(LinearLayout.java:634)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.View.measure(View.java:12892)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.View.measure(View.java:12892)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1249)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.View.measure(View.java:12892)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.View.measure(View.java:12892)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.widget.LinearLayout.measureVertical(LinearLayout.java:812)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.View.measure(View.java:12892)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-20 19:52:14.193: E/AndroidRuntime(3908): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2265)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.View.measure(View.java:12892)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1240)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2628)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.os.Handler.dispatchMessage(Handler.java:99)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.os.Looper.loop(Looper.java:137)
07-20 19:52:14.193: E/AndroidRuntime(3908): at android.app.ActivityThread.main(ActivityThread.java:4507)
07-20 19:52:14.193: E/AndroidRuntime(3908): at java.lang.reflect.Method.invokeNative(Native Method)
07-20 19:52:14.193: E/AndroidRuntime(3908): at java.lang.reflect.Method.invoke(Method.java:511)
07-20 19:52:14.193: E/AndroidRuntime(3908): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980)
07-20 19:52:14.193: E/AndroidRuntime(3908): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
07-20 19:52:14.193: E/AndroidRuntime(3908): at dalvik.system.NativeStart.main(Native Method)
I can't see a line where the exception is thrown so I can't figure it out quite good. I do know it is in these lines:
我看不到抛出异常的行，所以我无法弄清楚。我知道它在这些行中：
public class TodayFragment extends Fragment {
ListView listView;
String[] urls;
ActionBar mActionBar;
Spinner spinner1;
public TodayFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
LinearLayout linear = new LinearLayout(getActivity());
linear.setOrientation(LinearLayout.VERTICAL);
spinner1 = new Spinner(getActivity());
spinner1.setLayoutParams(new LayoutParams(
LinearLayout.LayoutParams.WRAP_CONTENT,
LinearLayout.LayoutParams.WRAP_CONTENT));
linear.addView(spinner1);
listView = new ListView(getActivity());
spinner1.setLayoutParams(new LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.WRAP_CONTENT));
linear.addView(listView);
new ParseHTML().execute();
return linear;
}
}
The fragment I'm using is android.support.v4.app.Fragment. What causes this?
我使用的片段是 android.support.v4.app.Fragment。这是什么原因造成的？
回答by ab11
Your import statement for LayoutParams is probably importing ViewGroup.LayoutParams. Try explicitly using LinearLayout.LayoutParams(...):
您的 LayoutParams 导入语句可能正在导入 ViewGroup.LayoutParams。尝试明确使用 LinearLayout.LayoutParams(...)：
spinner1.setLayoutParams(new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.WRAP_CONTENT,
LinearLayout.LayoutParams.WRAP_CONTENT));
回答by I?igo
Try setting LinearLayout's LayoutParams' before attatching any children.
在附加任何孩子之前尝试设置 LinearLayout 的 LayoutParams'。
LinearLayout linear = new LinearLayout(getActivity());
linear.setLayoutParams(new ViewGroup.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT));
linear.setOrientation(LinearLayout.VERTICAL);
回答by Maxime Ancelin
In case you're wondering which LayoutParams you must use for each View, look at this doc:
如果您想知道每个视图必须使用哪些 LayoutParams，请查看此文档：
Each view must have a LayoutParam acording to his parent.
每个视图必须有一个 LayoutParam 根据其父视图。
For example, in order to create this Views hierarhy,
例如，为了创建此视图层次结构，
- RelativeLayout relativeLayout
- LinearLayout linearLayout , orientation: vertical
- TextView textView
- Button button1
- Button button2
- 相对布局相对布局
- LinearLayout linearLayout ，方向：垂直
- 文本视图文本视图
- 按钮按钮 1
- 按钮按钮 2
replace the content of your onCreate method in your main activity with :
将主要活动中的 onCreate 方法的内容替换为：
super.onCreate(savedInstanceState);
RelativeLayout relativeLayout = new RelativeLayout(this);
LinearLayout linearLayout = new LinearLayout(this);
linearLayout.setOrientation(LinearLayout.VERTICAL);
linearLayout.setLayoutParams(new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.MATCH_PARENT));
relativeLayout.addView(linearLayout);
TextView textView = new TextView(this);
textView.setText("a text");
textView.setLayoutParams(new LinearLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
linearLayout.addView(textView);
Button button1 = new Button(this);
button1.setText("button 1");
button1.setLayoutParams(new LinearLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
linearLayout.addView(button1);
setContentView(relativeLayout);
