最近几天,我学习了如何使用 SQLiteOpenHelper 创建 SQLite 数据库并通过 RecyclerView 显示它。在 。是的,借助 google 和 Stack-overflow 的力量,我学得很好。但是,我现在无法通过 RecyclerView 显示外部数据库数据。过去两天我进行了很多搜索,大多数他们只是通过使用“资产文件夹和 SQLiteAssetsHelper 将外部数据库导入应用程序。还没有找到任何解释如何通过已导入的 RecyclerView 呈现数据的内容。所以,请你给我一些通过 RecyclerView 显示外部 SQLite 数据库数据的指南吗?任何链接或任何书籍或任何参考都将不胜感激。提前致谢。
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作为您与数据库交互的结果,使用应该得到一个数据集(一个数组,或像 ArrayList 这样的集合)。正如我所看到的,从您的解释中,您现在知道如何获取它,但不知道如何将其传递给您的 recyclerView。所以你需要一个适配器来做到这一点。Adapter 是一个类,它将从您的数组数据集中获取每个对象,并从它的数据中创建(膨胀)单个 recyclerView 项目。在处理完所有数组项后,适配器将创建一个项列表,这样它就会用数据填充您的回收器视图,这是一个代码片段,可以帮助您理解它是如何工作的:
<android.support.v7.widget.RecyclerView
android:id="@+id/my_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private String[] mDataset;
// Provide a reference to the views for each data item
// Complex data items may need more than one view per item, and
// you provide access to all the views for a data item in a view holder
public static class MyViewHolder extends RecyclerView.ViewHolder {
// each data item is just a string in this case
public TextView textView;
public MyViewHolder(TextView v) {
super(v);
textView = v;
}
}
// Provide a suitable constructor (depends on the kind of dataset)
public MyAdapter(String[] myDataset) {
mDataset = myDataset;
}
// Create new views (invoked by the layout manager)
@Override
public MyAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
// create a new view
TextView v = (TextView) LayoutInflater.from(parent.getContext())
.inflate(R.layout.my_text_view, parent, false);
...
MyViewHolder vh = new MyViewHolder(v);
return vh;
}
// Replace the contents of a view (invoked by the layout manager)
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
// - get element from your dataset at this position
// - replace the contents of the view with that element
holder.textView.setText(mDataset[position]);
}
// Return the size of your dataset (invoked by the layout manager)
@Override
public int getItemCount() {
return mDataset.length;
}
}
public class MyActivity extends Activity {
private RecyclerView recyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager layoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_activity);
recyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
recyclerView.setHasFixedSize(true);
// use a linear layout manager
layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
// specify an adapter (see also next example)
mAdapter = new MyAdapter(myDataset);
recyclerView.setAdapter(mAdapter);
}
// ...
}
于 2019-04-02T20:03:48.107 回答