1.inflate方法
public View inflate(@LayoutRes int resource, @Nullable ViewGroup root) {
return inflate(resource, root, root != null);
}
if (TAG_MERGE.equals(name)) {
if (root == null || !attachToRoot) {
throw new InflateException("<merge /> can be used only with a valid "
+ "ViewGroup root and attachToRoot=true");
}
rInflate(parser, root, inflaterContext, attrs, false);
} else {
// Temp is the root view that was found in the xml
final View temp = createViewFromTag(root, name, inflaterContext, attrs);
ViewGroup.LayoutParams params = null;
if (root != null) {
if (DEBUG) {
System.out.println("Creating params from root: " +
root);
}
// Create layout params that match root, if supplied
params = root.generateLayoutParams(attrs);
if (!attachToRoot) {
// Set the layout params for temp if we are not
// attaching. (If we are, we use addView, below)
temp.setLayoutParams(params);
}
}
if (DEBUG) {
System.out.println("-----> start inflating children");
}
// Inflate all children under temp against its context.
rInflateChildren(parser, temp, attrs, true);
if (DEBUG) {
System.out.println("-----> done inflating children");
}
// We are supposed to attach all the views we found (int temp)
// to root. Do that now.
if (root != null && attachToRoot) {
root.addView(temp, params);
}
// Decide whether to return the root that was passed in or the
// top view found in xml.
if (root == null || !attachToRoot) {
result = temp;
}
}
2.fragment
public class HomeCombinationFragment extends Fragment {
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
// container 写不写都一样，布局没有改变 布局中设置高度这些都没有影响
View view = inflater.inflate(R.layout.fragment_home_combination,container,false);
return view;
}
}
3.recyclerView
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
// 没有传viewGroup 无法加载layout.xml中的params，比如宽高，margin等
View view = LayoutInflater.from(context).inflate(R.layout.item_smoth_num_layout,null);
return new MyViweHolder(view);
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
// 正确的
View view = LayoutInflater.from(context).inflate(R.layout.item_smoth_num_layout,viewGroup,false);
return new MyViweHolder(view);
}
错误
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
// 传viewGroup 没有设置attachToRoot为false 报错
View view = LayoutInflater.from(context).inflate(R.layout.item_smoth_num_layout,viewGroup);
return new MyViweHolder(view);
}
如下是错误日志
2020-07-31 16:21:32.955 30175-30175/com.example.uxin.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.uxin.myapplication, PID: 30175
java.lang.IllegalStateException: ViewHolder views must not be attached when created. Ensure that you are not passing 'true' to the attachToRoot parameter of LayoutInflater.inflate(..., boolean attachToRoot)
at android.support.v7.widget.RecyclerView$Adapter.createViewHolder(RecyclerView.java:6796)
at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5975)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5858)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5854)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2230)
at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1557)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1517)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:612)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3924)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3641)
at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:4194)
at android.view.View.layout(View.java:19692)
5.如果fragment设置为attachToroot为true，会出现栈溢出；
public class HomeCombinationFragment extends Fragment {
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
// 栈溢出
View view = inflater.inflate(R.layout.fragment_home_combination,container);
return view;
}
}
栈溢出
2020-07-31 15:35:11.377 26996-26996/com.example.uxin.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.uxin.myapplication, PID: 26996
java.lang.StackOverflowError: stack size 8MB
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6958)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
at android.view.ViewGroup.jumpDrawablesToCurrentState(ViewGroup.java:6962)
6.这个我fragment没有获取不到出现的问题，比如getItem方法返回的为null
2020-07-31 14:16:16.063 8711-8711/com.example.uxin.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.uxin.myapplication, PID: 8711
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Class java.lang.Object.getClass()' on a null object reference
at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:396)
at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:391)
at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:107)
at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:1010)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1158)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1092)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1622)
at android.view.View.measure(View.java:22104)
at android.support.constraint.ConstraintLayout.internalMeasureChildren(ConstraintLayout.java:1227)
at android.support.constraint.ConstraintLayout.onMeasure(ConstraintLayout.java:1572)
at android.view.View.measure(View.java:22104)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6584)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at android.view.View.measure(View.java:22104)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6584)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1514)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:806)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:685)
at android.view.View.measure(View.java:22104)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6584)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at com.android.internal.policy.DecorView.onMeasure(DecorView.java:722)
at android.view.View.measure(View.java:22104)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2447)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1528)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1781)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1416)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6845)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:966)
at android.view.Choreographer.doCallbacks(Choreographer.java:778)
at android.view.Choreographer.doFrame(Choreographer.java:713)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:952)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6798)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
image.png
7.自定义view中，如果view继承的是LinearLayout等ViewGroup，为了减少层级，自定义view中的布局的跟布局可以用merge；
public class MyCommonView extends LinearLayout implements ICommonView {
public MyCommonView(Context context) {
this(context, null);
}
public MyCommonView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
}
public MyCommonView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mContext = context;
//此时 root必须填this，attachToRoot必须为true才可以把布局中inflate的view，addView到自定义view中，进而展示在界面视图中；
// 可以把item_radio_player_layout布局的跟布局设置为merge，减少一个层级，但是如果该为merge，在跟布局上的padding设置将会不起作用，需要代码设置padding
View view = LayoutInflater.from(context).inflate(R.layout.item_radio_player_layout, null, true);
}
}
原始布局xml，跟布局有padding设置
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="180dp"
android:paddingLeft="12dp"
android:paddingRight="12dp"
android:paddingTop="10dp"
android:paddingBottom="10dp">
<include android:id="@+id/pwcv_cover_view"
layout="@layout/view_radio_player_cover_layout"/>
<LinearLayout
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1"
android:layout_toRightOf="@id/pwcv_cover_view"
android:orientation="vertical">
......省略
</LinearLayout>
</LinearLayout>
如果把LinearLayout该为merge，布局中padding设置将失效，需要代码设置padding
public MyCommonView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mContext = context;
// 可以把item_radio_player_layout布局的跟布局设置为merge，减少一个层级
View view = LayoutInflater.from(context).inflate(R.layout.item_radio_player_layout, this, true);
int i = CommonUtils.dip2px(mContext, 12);
// 设置padding
setPadding(i,i,i,i);
}
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