Question

我的主要活动是从SharedPreferences中保存并加载一些数据......到目前为止我已经能够这样做了。

这些是我的onCreate，onPause和OnResume方法。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    setTitle(R.string.title_activity_main);

    this.spinner = (Spinner) findViewById(R.id.geomObject);
    this.sbWidth = (SeekBar) findViewById(R.id.widthSB);
    this.sbDepth = (SeekBar) findViewById(R.id.depthSB);
    this.sbHeight = (SeekBar) findViewById(R.id.heightSB);
    this.widthProgress = (TextView) findViewById(R.id.widthDisplay);
    this.depthProgress = (TextView) findViewById(R.id.depthDisplay);
    this.heightProgress = (TextView) findViewById(R.id.heightDisplay);

    ...more code...
}

protected void onResume() {
    super.onResume();
    loadPrefs();
}

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

这些是我完成大部分工作的方法，因此我可以保持onX方法的清洁：

private void savePrefs() {
    this.width = this.sbWidth.getProgress();
    this.depth = this.sbDepth.getProgress();
    this.height = this.sbHeight.getProgress();
    this.forma = this.spinner.getSelectedItemPosition();

    getSharedPreferences("SEEKBARS", MODE_PRIVATE).edit().putInt("width", width).commit();
    getSharedPreferences("SEEKBARS", MODE_PRIVATE).edit().putInt("depth", depth).commit();
    getSharedPreferences("SEEKBARS", MODE_PRIVATE).edit().putInt("height", height).commit();
    getSharedPreferences("SEEKBARS", MODE_PRIVATE).edit().putInt("forma", forma).commit();
    getSharedPreferences("LOCKBARS", MODE_PRIVATE).edit().putBoolean("lockbars", menuLock.isChecked()).commit();
}

private void loadPrefs() {
    int savedSpinner = getSharedPreferences("SEEKBARS", MODE_PRIVATE).getInt("forma", SPINNER_DEFAULT);
    int savedWidth = getSharedPreferences("SEEKBARS", MODE_PRIVATE).getInt("width", SEEKBAR_DEFAULT);
    int savedDepth = getSharedPreferences("SEEKBARS", MODE_PRIVATE).getInt("depth", SEEKBAR_DEFAULT);
    int savedHeight = getSharedPreferences("SEEKBARS", MODE_PRIVATE).getInt("height", SEEKBAR_DEFAULT);

    boolean savedLockFlag = getSharedPreferences("LOCKBARS", MODE_PRIVATE).getBoolean("lockbars", false);

    this.spinner.setSelection(savedSpinner);
    this.sbWidth.setProgress(savedWidth);
    this.sbDepth.setProgress(savedDepth);
    this.sbHeight.setProgress(savedHeight);
//This is the line raising the exception Display:
        this.menuLock.setChecked(savedLockFlag); 


        this.widthProgress.setText(String.valueOf(savedWidth) + " " + getResources().getString(R.string.blocks));
        this.depthProgress.setText(String.valueOf(savedDepth) + " " + getResources().getString(R.string.blocks));
        this.heightProgress.setText(String.valueOf(savedHeight) + " " + getResources().getString(R.string.blocks));
    }

我没看到错误在哪里。我一直在搜索，我知道我无法在onCreate上调用getSharedPreferences，这就是我在onResume上执行此操作的原因。怎么了？

我还附上了logcat，以防万一：

FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to resume activity {es.nirvash.android.msg/es.nirvash.android.msg.MainActivity}: java.lang.NullPointerException
    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2567)
    at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2595)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2109)
    at android.app.ActivityThread.access$600(ActivityThread.java:132)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1157)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:137)
    at android.app.ActivityThread.main(ActivityThread.java:4575)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:511)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
    at es.nirvash.android.msg.MainActivity.loadPrefs(MainActivity.java:231)
    at es.nirvash.android.msg.MainActivity.onResume(MainActivity.java:147)
    at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1154)
    at android.app.Activity.performResume(Activity.java:4539)
    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2557)
    ... 12 more

Answer 1

问题不是你的布尔值，而是变量menuLock。 boolean（基本类型）不能是null。

查找声明menuLock的位置，并确保其中包含要保留的内容。这样，使用它时它不会为null。当然，如果它是View，请在onCreate()之后setContentView()中为其分配一些内容，因为它具有“活动”布局并创建了保证。

SharedPreferences返回null，即使它具有默认值

1 个答案: