如何在重新打开应用程序后检索editText保存的值

Question

我创建了一个listview活动，它在项目单击时打开对话框。在对话框中，用户可以输入不同的值，这些值保存在同一列表视图项的textView中。这是完美的，问题是如果我关闭应用程序，当我再次打开它时，保存的值就不存在了。关闭应用程序后如何保持值？谢谢

NoteAdapter.java

        package com.cngcnasaud.orar;
import java.util.Arrays;
import android.app.Dialog;
import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;
public class NoteAdapter extends BaseAdapter {
    String[] result;
    Context context;
    int[] imageId;
    private static LayoutInflater inflater = null;
    private Dialog dialog;
    String[] savedEntries;
    String[] saved = null;
    public NoteAdapter(Note note, String[] prgmNameList, String[] saved) {
        // TODO Auto-generated constructor stub
        result = prgmNameList;
        context = note;
        inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (saved == null) {
            savedEntries = new String[result.length];
            Arrays.fill(savedEntries, "");
        } else
            savedEntries = saved;
    }
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return result.length;
    }
    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return savedEntries[position];
    }
    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }
    public class Holder {
        TextView tv;
        ImageView img;
        public TextView text;
    }
    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        final Holder holder = new Holder();
        View rowView;
        rowView = inflater.inflate(R.layout.note_items, null);
        holder.tv = (TextView) rowView.findViewById(R.id.textView1);
        holder.text = (TextView) rowView.findViewById(R.id.textView2);
        holder.text.setText(savedEntries[position]);
        holder.img = (ImageView) rowView.findViewById(R.id.imageView1);
        rowView.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                dialog = new Dialog(context);
                dialog.setContentView(R.layout.dialog);
                dialog.setTitle("Materie:" + result[position]);
                final EditText txtMode = (EditText) dialog
                        .findViewById(R.id.dialog);
                Button btnSave = (Button) dialog.findViewById(R.id.bsave);
                btnSave.setOnClickListener(new OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        String data = txtMode.getText().toString();
                        holder.text.setText(data);
                        savedEntries[position] = data;
                        dialog.dismiss();
                        Log.d("data", data);
                    }
                });
                dialog.show();
            }
        });
        return rowView;
    }
}

注意.java：

    package com.cngcnasaud.orar;
import java.util.ArrayList;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.view.Menu;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
public class Note extends Activity {
    public static final ListAdapter NoteAdapter = null;
    ListView lv;
    Context context;
    ArrayList<?> prgmName;
    TextView text;
    public static String[] prgmNameList = { "Romana   - ", "Matematica   - ",
            "Lb. Engleza   - ", "Lb. Germana/Franceza - ", "Istorie   - ",
            "Geografie   - ", "Biologie   - ", "Fizica   - ", "Ed. Fizica   - " };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.note_listview);
        text = (TextView) findViewById(R.id.textView2);
        context = this;
        lv = (ListView) findViewById(R.id.listView);
        lv.setAdapter(new NoteAdapter(this, prgmNameList, null));
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
    @Override
    protected void onStop() {
        // TODO Auto-generated method stub
        NoteAdapter adapter = (NoteAdapter) lv.getAdapter();
        // Variable is public for clarity.
        String toSave = EncodeDecode.encode(adapter.savedEntries);
        SharedPreferences.Editor editor = getSharedPreferences("LV Data",
                MODE_PRIVATE).edit();
        editor.putString("TVEntries", toSave);
        editor.commit();
    }
    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        SharedPreferences prefs = getSharedPreferences("LV Data", MODE_PRIVATE);
        String encoded = prefs.getString("TVEntries", "");
        String[] entries;
        if (encoded.equals(""))
            entries = null;
        else
            entries = EncodeDecode.decode(encoded);
        NoteAdapter adapter = (NoteAdapter) lv.getAdapter();
        adapter.savedEntries = entries;
        lv.setAdapter(adapter);
        super.onResume();
    }
}

Answer 1

以下是一个涉及SharedPreferences:的拟议解决方案

• 首先，向Adapter类中添加一个String[]实例变量。这将包含你想要保存的内容（TextViews中的字段。初始化你的构造函数。

  public NoteAdapter(Note note, String[] saved, String[] prgmNameList, int[] prgmImages) {
    result=prgmNameList;
    context=note;
    imageId=prgmImages;
    inflater = ( LayoutInflater )context.
           getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    /**********INSERTED CODE********/
    if(saved == null) {
      savedEntries = new String[result.length];`
      Arrays.fill(savedEntires, "");
    }
    else
      savedEntries = saved;
    /****************************/
  
  }
  

• 还要修改overriden getItem()方法，以在savedEntires:中返回适当的元素

  @Override
  public Object getItem(int position) {
   return savedEntries[position];
  }
  

• 无论何时更新TextView，都要相应地更新列表：

  @Override
  public void onClick(View v) {
    String data = txtMode.getText().toString();
    holder.text.setText(data);
    /***INSERTED CODE****/  
    savedEntries[position] = data;
    /*******************/
    dialog.dismiss();
    Log.d("data", data);
  }
  

• 我们将使用字符串对将此数组保存在SharedPreferences中。由于字符串可能包含任何字符，因此很难/低效地找到单个分隔符。我实现了一个名为EncodeDecode的类，它可以将String数组编码为单个格式化的String，并在此处将其解码回String数组：https://gist.github.com/liangricha/10759438.我将使用这个类来转换/取消转换savedEntries。

• 每当您想保存savedEntries（在onStop()中）时，只需执行以下代码：

  ListView lv = //... get reference
  NoteAdapter adapter = (NoteAdapter)lv.getAdapter();
  //Variable is public for clarity.
  String toSave = EncodeDecode.encode(adapter.savedEntries);
  SharedPreferences.Editor editor = getSharedPreferences("LV Data", MODE_PRIVATE).editor();
  editor.putString("TVEntries", toSave);
  editor.commit();
  

• 当您想要检索TextView条目的字符串数组（在onResume()中）时，执行：

  SharedPreferences prefs = getSharedPreferences("LV Data", MODE_PRIVATE);
  String encoded = prefs.getString("TVEntries", "");
  String[] entries
  if(encoded.equals(""))
    entries = null;
  else
    entries = EncodeDeocde.decode(encoded);
  NoteAdapter adapter = (NoteAdapter)lv.getAdapter();
  adapter.savedEntries = entries;
  lv.setAdapter(adapter);
  

  然后，在"NoteAdapter"的getView()方法中，将TextView的字段设置为savedEntries:中的相应条目

   holder.text.setText(savedEntries[position]);