我目前正在开发一个使用RecyclerView的应用程序。
在审核LogCat时,我注意到 onCreateViewHolder 在实例化后被调用了两次。
09-22 05:22:55.209 V/Adapter﹕ Construct
09-22 05:22:55.213 V/Adapter﹕ onCreateViewHolder
09-22 05:22:55.224 V/Adapter﹕ onBindViewHolder
09-22 05:22:55.240 V/Adapter﹕ onCreateViewHolder
09-22 05:22:55.247 V/Adapter﹕ onBindViewHolder
同样onBindViewHolder被调用了两次,虽然我知道每当项目被回收时都会被调用。
但我认为onCreateViewHolder只需调用一次即可。
这是不正常的行为吗?如果是这样,怎么解决?
答案 0 :(得分:19)
这不是异常,而是非常正常的行为。你不必担心。
ViewHolder确实会被回收,不会再次重新创建。
但是,在应用程序的屏幕上显示多个项目需要多个ViewHolders 。因此会创建一定数量的ViewHolders,因此onCreateViewHolder会被调用一段时间。
只要数据重置为ViewHolders之一,就会无限调用onBindViewHolder。
我用下面的测试应用程序检查了这个事实:
MainActivity:
public class MainActivity extends AppCompatActivity {
private static final String[] DATASET = new String[]{
"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m",
"n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z",
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
recyclerView.setHasFixedSize(true);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
MyAdapter myAdapter = new MyAdapter(DATASET);
recyclerView.setAdapter(myAdapter);
}
}
MyAdapter:
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private static final String LOG_TAG = "RecyclerViewAdapter";
private String[] dataset;
private int counterOnCreateViewHolder = 0;
private int counterOnBindViewHolder = 0;
public MyAdapter(String[] dataset) {
Log.d(LOG_TAG, "Construct");
this.dataset = dataset;
}
public static class ViewHolder extends RecyclerView.ViewHolder {
public TextView textView;
public ViewHolder(TextView textView) {
super(textView);
this.textView = textView;
}
}
@Override
public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
Log.d(LOG_TAG, "onCreateViewHolder (" + ++counterOnCreateViewHolder + ")");
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.adapter_textview, parent, false);
ViewHolder viewHolder = new ViewHolder((TextView) view);
return viewHolder;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Log.d(LOG_TAG, "onBindViewHolder (" + ++counterOnBindViewHolder + ")");
holder.textView.setText(dataset[position]);
}
@Override
public int getItemCount() {
// Log.d(LOG_TAG, "getItemCount");
return dataset.length;
}
}
布局/ activity_main.xml中:
<android.support.v7.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical"
android:id="@+id/recycler_view" />
布局/ adapter_textview.xml:
<TextView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/adapter_textview"
android:textSize="30sp" />
结果:
09-22 06:03:04.166 D/RecyclerViewAdapter﹕ Construct
09-22 06:03:05.179 D/RecyclerViewAdapter﹕ onCreateViewHolder (1)
09-22 06:03:05.183 D/RecyclerViewAdapter﹕ onBindViewHolder (1)
09-22 06:03:05.190 D/RecyclerViewAdapter﹕ onCreateViewHolder (2)
09-22 06:03:05.192 D/RecyclerViewAdapter﹕ onBindViewHolder (2)
09-22 06:03:05.192 D/RecyclerViewAdapter﹕ onCreateViewHolder (3)
09-22 06:03:05.194 D/RecyclerViewAdapter﹕ onBindViewHolder (3)
09-22 06:03:05.195 D/RecyclerViewAdapter﹕ onCreateViewHolder (4)
09-22 06:03:05.197 D/RecyclerViewAdapter﹕ onBindViewHolder (4)
09-22 06:03:05.198 D/RecyclerViewAdapter﹕ onCreateViewHolder (5)
09-22 06:03:05.199 D/RecyclerViewAdapter﹕ onBindViewHolder (5)
09-22 06:03:05.200 D/RecyclerViewAdapter﹕ onCreateViewHolder (6)
09-22 06:03:05.202 D/RecyclerViewAdapter﹕ onBindViewHolder (6)
09-22 06:03:05.203 D/RecyclerViewAdapter﹕ onCreateViewHolder (7)
09-22 06:03:05.204 D/RecyclerViewAdapter﹕ onBindViewHolder (7)
09-22 06:03:05.206 D/RecyclerViewAdapter﹕ onCreateViewHolder (8)
09-22 06:03:05.207 D/RecyclerViewAdapter﹕ onBindViewHolder (8)
09-22 06:03:05.209 D/RecyclerViewAdapter﹕ onCreateViewHolder (9)
09-22 06:03:05.211 D/RecyclerViewAdapter﹕ onBindViewHolder (9)
09-22 06:03:05.212 D/RecyclerViewAdapter﹕ onCreateViewHolder (10)
09-22 06:03:05.213 D/RecyclerViewAdapter﹕ onBindViewHolder (10)
09-22 06:03:05.215 D/RecyclerViewAdapter﹕ onCreateViewHolder (11)
09-22 06:03:05.217 D/RecyclerViewAdapter﹕ onBindViewHolder (11)
09-22 06:03:05.218 D/RecyclerViewAdapter﹕ onCreateViewHolder (12)
09-22 06:03:05.220 D/RecyclerViewAdapter﹕ onBindViewHolder (12)
09-22 06:03:55.048 D/RecyclerViewAdapter﹕ onCreateViewHolder (13)
09-22 06:03:55.050 D/RecyclerViewAdapter﹕ onBindViewHolder (13)
09-22 06:03:55.228 D/RecyclerViewAdapter﹕ onCreateViewHolder (14)
09-22 06:03:55.229 D/RecyclerViewAdapter﹕ onBindViewHolder (14)
09-22 06:03:55.230 D/RecyclerViewAdapter﹕ onCreateViewHolder (15)
09-22 06:03:55.231 D/RecyclerViewAdapter﹕ onBindViewHolder (15)
09-22 06:03:55.232 D/RecyclerViewAdapter﹕ onBindViewHolder (16)
09-22 06:03:55.232 D/RecyclerViewAdapter﹕ onBindViewHolder (17)
09-22 06:03:55.260 D/RecyclerViewAdapter﹕ onBindViewHolder (18)
09-22 06:03:55.276 D/RecyclerViewAdapter﹕ onBindViewHolder (19)
09-22 06:03:55.296 D/RecyclerViewAdapter﹕ onBindViewHolder (20)
09-22 06:03:55.310 D/RecyclerViewAdapter﹕ onBindViewHolder (21)
如您所见,仅在onCreateViewHolder (15)
之后调用onBindViewHolder。
答案 1 :(得分:4)
以下是针对RecyclerView稳定视图的稳定答案
下面的这些行有助于垂直地在recyclerview中保持列表数据的一致性 在我的垂直列表中,只有10个我不想再次绑定的项目。 每行都有无限的水平RecyclerView列表。
mRecyclerview.getRecycledViewPool()。setMaxRecycledViews(int viewtype,int itemsCount)
mRecyclerview.setItemViewCacheSize(int itemsCount)
这两种方法都有助于不回收垂直视图。 但是如果list太大,则会导致OOM错误,因此请谨慎实施。
Here 0 is viewType in Recyclerview adapter and 10 are the items count.
mRecyclerview.getRecycledViewPool().setMaxRecycledViews(0, 10);
mRecyclerview.setItemViewCacheSize(10);
答案 2 :(得分:0)
您可以通过此代码增加RecycledViewPool计数。默认情况下它有5个。
你可以根据需要增加。
recyclerView.getRecycledViewPool()。setMaxRecycledViews(0,50); // 0 - 您的视图类型