java - 尝试保存 EditText 时无法暂停

Question

Stack 的人们大家好...... 我试图让我的应用程序使用 EditText 框保存文本，以便当用户关闭应用程序并重新打开它时，输入字段会保持保存状态，但我收到一个 NPE 当点击我的按钮时。

请帮助我:)

package com.smarte.smartipcontrol;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class IPEntry extends Activity {
    public final static String ACTUALSMARTIP = "com.smarte.smartipcontrol.ACTU_IP";
    private EditText editText;
    private EditText editText2;

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.act_ipentry, menu);
        return true;
    }

    /** Called when the user clicks the SendIP button */
    public void sendip(View view) {
        Intent intent = new Intent(this, IPControl.class);
        EditText editText = (EditText) findViewById(R.id.serverIpAddress);
        String actu_ip = editText.getText().toString();
        intent.putExtra(ACTUALSMARTIP, actu_ip);
        startActivity(intent);
    }

    protected void onResume() {
        super.onResume();
        SharedPreferences prefs = getPreferences(0); 
        String restoredText = prefs.getString("text", null);
        if (restoredText != null) {
            editText.setText(restoredText, TextView.BufferType.EDITABLE);

            int selectionStart = prefs.getInt("selection-start", -1);
            int selectionEnd = prefs.getInt("selection-end", -1);
            if (selectionStart != -1 && selectionEnd != -1) {
                editText.setSelection(selectionStart, selectionEnd);
            }
            SharedPreferences prefs2 = getPreferences(1); 
            String restoredText2 = prefs2.getString("text2", null);
            if (restoredText2 != null) {
                editText2.setText(restoredText2, TextView.BufferType.EDITABLE);

                int selectionStart2 = prefs2.getInt("selection-start2", -1);
                int selectionEnd2 = prefs2.getInt("selection-end2", -1);
                if (selectionStart2 != -1 && selectionEnd2 != -1) {
                    editText2.setSelection(selectionStart2, selectionEnd2);
                }
            }
        }
    }

    protected void onPause() {
        super.onPause();

        SharedPreferences.Editor editor = getPreferences(0).edit();
        editor.putString("text", editText.getText().toString());
        editor.putInt("selection-start", editText.getSelectionStart());
        editor.putInt("selection-end", editText.getSelectionEnd());
        editor.commit();

        SharedPreferences.Editor editor2 = getPreferences(1).edit();
        editor2.putString("text2", editText2.getText().toString());
        editor2.putInt("selection-start2", editText2.getSelectionStart());
        editor2.putInt("selection-end2", editText2.getSelectionEnd());
        editor2.commit();
    }   
}

日志猫

12-17 13:20:20.043: E/AndroidRuntime(1069): FATAL EXCEPTION: main
12-17 13:20:20.043: E/AndroidRuntime(1069): java.lang.RuntimeException: Unable to pause activity {com.smarte.smartipcontrol/com.smarte.smartipcontrol.IPEntry}: java.lang.NullPointerException
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3016)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2971)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:2949)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.app.ActivityThread.access$800(ActivityThread.java:141)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1245)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.os.Looper.loop(Looper.java:137)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.app.ActivityThread.main(ActivityThread.java:5039)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at java.lang.reflect.Method.invokeNative(Native Method)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at java.lang.reflect.Method.invoke(Method.java:511)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at dalvik.system.NativeStart.main(Native Method)
12-17 13:20:20.043: E/AndroidRuntime(1069): Caused by: java.lang.NullPointerException
12-17 13:20:20.043: E/AndroidRuntime(1069):     at com.smarte.smartipcontrol.IPEntry.onPause(IPEntry.java:72)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.app.Activity.performPause(Activity.java:5206)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.app.Instrumentation.callActivityOnPause(Instrumentation.java:1226)
12-17 13:20:20.043: E/AndroidRuntime(1069):     at android.app.ActivityThread.performPauseActivity(ActivityThread.java:3002)
12-17 13:20:20.043: E/AndroidRuntime(1069):     ... 12 more

Answer 1

我从未见过您实例化 editText2，一旦您检查第 72 行，您可能会得到确认:at com.smarte.smartipcontrol.IPEntry.onPause(IPEntry.java: 72) (也可以是 editText，请参阅我的编辑)。

由于 editText 和 editText2 (顺便说一句，名称选择不佳)是全局变量，因此您应该在 onCreate() 中实例化它们:

editText = (EditText) findViewById(R.id.serverIpAddress);
editText2 = (EditText) findViewById(R.id.theSecondEditText);

编辑:顺便说一句，在sendIp中，您正在实例化一个本地变量editText，这意味着不只有editText2是null，editText也是null!您不应该永远使用相同名称的全局变量和局部变量(构造函数除外，然后使用 this 关键字)。