Question

我在android中创建一个简单的笔记应用程序。我基本上使用两个名为Main Page和Second Activity的活动类。我在第二个活动中将一些数据存储在共享首选项中，并希望在我的第一个活动中使用它。我将数据作为（String，Integer）密钥对存储在共享首选项中。在我的主要活动类中，当我从共享首选项中获取值为Integer并将其与值0进行比较时，我得到一个异常，即java.lang.string不能被强制转换为java .lang.integer。我不知道为什么会出现这种异常。 Android工作室没有给我一个例外但是当我运行我的应用程序时，我的应用程序崩溃了。我附上了代码供参考。

MainActivity类：

package com.example.prateeksharma.noteballondor;

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;


public class MainPage extends ActionBarActivity {

    Notes notes = null;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_page);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main_page, menu);
        return true;
    }

    @Override
    protected void onResume() {
        super.onResume();
        SharedPreferences sharedPreferences = getSharedPreferences("com.example.prateeksharma.noteballondor", Context.MODE_PRIVATE);
        //Map<String, Integer> notesMap = (Map<String, Integer>)sharedPreferences.getAll();
        List<Notes> listNotes = new ArrayList<>();
        Map<String, ?> prefsMap = sharedPreferences.getAll();
        for (Map.Entry<String, ?> entry: prefsMap.entrySet()) {
            if (entry.getValue() == 0){
                notes = new Notes();
            }
            notes.setNoteText(entry.getKey());
            listNotes.add(notes);
            sharedPreferences.edit().putInt(entry.getKey(),2);
        }
        NotesArrayAdapter  notesArrayAdapter = new NotesArrayAdapter(this,R.layout.list_layout, listNotes);
        final ListView listview = (ListView) findViewById(R.id.listView);
        listview.setAdapter(notesArrayAdapter);
        listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
/**/
            @Override
            public void onItemClick(AdapterView<?> parent, final View view,
                                    int position, long id) {
                notes = (Notes) parent.getItemAtPosition(position);
                Intent intent = new Intent(MainPage.this, SecondActivity.class);
                intent.putExtra("Notes",notes);
                startActivity(intent);
            }
        });

    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        switch (item.getItemId()) {
            case R.id.new_link:
                Intent intent = new Intent(this, SecondActivity.class);
                intent.putExtra("Notes",(android.os.Parcelable)null);
                startActivity(intent);
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }

    }
}

SecondActivity类：

package com.example.prateeksharma.noteballondor;

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;


public class SecondActivity extends ActionBarActivity {

    public SharedPreferences sharedPreferences;
    SharedPreferences.Editor edit;
    Notes notes;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        sharedPreferences = getSharedPreferences("com.example.prateeksharma.noteballondor", Context.MODE_PRIVATE);
        edit = sharedPreferences.edit();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_second, menu);
        return true;
    }


    @Override
    protected void onResume() {
        super.onResume();
        Intent intent = getIntent();
        notes = (Notes)intent.getParcelableExtra("Notes");
        EditText editText = (EditText) findViewById(R.id.editText);
        if(notes != null){
            editText.setText(notes.getNoteText());
        }
        else{
            editText.setText(null);
        }

    }

    @Override
    protected void onStop() {
        super.onStop();
        getIntent().removeExtra(notes.getNoteText());
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        Intent intent = getIntent();

        //noinspection SimplifiableIfStatement
        switch (item.getItemId()) {
            case R.id.save:
                EditText editText = (EditText)findViewById(R.id.editText);
                if (notes != null){
                    edit.putInt(String.valueOf(editText.getText()),1);
                }
                else{
                    edit.putInt(String.valueOf(editText.getText()),0);
                }
                edit.commit();
                return true;
            case R.id.delete:
                if(notes != null){
                    edit.remove(notes.getNoteText());
                    edit.commit();
                    finish();
                    return true;
                }

            default:
                return super.onOptionsItemSelected(item);
        }
    }
}

我正在使用的笔记课程：

package com.example.prateeksharma.noteballondor;

import android.os.Parcel;
import android.os.Parcelable;

/**
 * Created by Dell on 02-06-2015.
 */
    public class Notes implements Parcelable {

        private String noteText;

        public String getNoteText() {
            return noteText;
        }

        public void setNoteText(String noteText) {
            this.noteText = noteText;
        }


        private Notes(Parcel in) {
            noteText = in.readString();
        }

        public Notes(){

        }

        @Override
        public int describeContents() {
            return 0;
        }

        @Override
        public void writeToParcel(Parcel dest, int flags) {
            dest.writeString(noteText);
        }

        @SuppressWarnings("unused")
        public static final Parcelable.Creator<Notes> CREATOR = new Parcelable.Creator<Notes>() {
            @Override
            public Notes createFromParcel(Parcel in) {
                return new Notes(in);
            }

            @Override
            public Notes[] newArray(int size) {
                return new Notes[size];
            }
        };
    }

有人可以告诉我为什么在这一行的MainActivity类中会出现此错误 if（entry.getValue（）== 0）

谢谢..

Answer 1

尝试替换

if ((Integer)entry.getValue() == 0){

使用

If((Integer.parseInt( entry.getValue()) ==0){

获取Cast Exception Android

1 个答案: