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我在 onCreate() 方法中设置了一个条件来检查是否存在一些以前的数据。但它不起作用。请指导我。而且我不想对 this.d 使用 onRestoreSavedState() 方法

public class ActivityOne extends Activity {

当您在重新配置之间保存状态时，将它们用作键

private static final String RESTART_KEY = "restart";
private static final String RESUME_KEY = "resume";
private static final String START_KEY = "start";
private static final String CREATE_KEY = "create";

LogCat 文档的字符串

private final static String TAG = "Lab-ActivityOne";
private int mCreate=0, mRestart=0, mStart=0, mResume=0;

当它们相应的生命周期方法被调用时，您将需要增加这些变量的值。

TODO：为每个 TextView 创建变量

private TextView mTvCreate, mTvRestart, mTvStart, mTvResume;

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

TODO：将适当的 TextView 分配给 TextView 变量

    mTvCreate=(TextView)findViewById(R.id.create);
    mTvRestart=(TextView)findViewById(R.id.restart);
    mTvResume=(TextView)findViewById(R.id.resume);
    mTvStart=(TextView)findViewById(R.id.start);


    Button launchActivityTwoButton = (Button) findViewById(R.id.bLaunchActivityTwo);
    launchActivityTwoButton.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

           Intent intent=null;
            intent = new Intent(v.getContext(),ActivityTwo.class);
        startActivity(intent);

        }
    });
    if(savedInstanceState!=null){
        mCreate=savedInstanceState.getInt(String.valueOf(mCreate));
        mRestart=savedInstanceState.getInt(String.valueOf(mRestart));
        mResume=savedInstanceState.getInt(String.valueOf(mResume));
        mStart=savedInstanceState.getInt(String.valueOf(mStart));
    }


    // Emit LogCat message
    Log.i(TAG, "Entered the onCreate() method");
        mCreate++;
        displayCounts();
}

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {

用一组键值对保存状态信息 4 行代码，每个计数变量一个 super.onSaveInstanceState(savedInstanceState);

    savedInstanceState.putInt(String.valueOf(mCreate),mCreate);
    savedInstanceState.putInt(String.valueOf(mRestart),mRestart);
    savedInstanceState.putInt(String.valueOf(mResume),mResume);
    savedInstanceState.putInt(String.valueOf(mStart),mStart);

}

更新显示的计数器 此方法要求计数器和 TextView 变量使用上面指定的名称 public void displayCounts() {

    mTvCreate.setText("onCreate() calls: " + mCreate);
    mTvStart.setText("onStart() calls: " + mStart);
    mTvResume.setText("onResume() calls: " + mResume);
    mTvRestart.setText("onRestart() calls: " + mRestart);

}

}

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1 回答 1

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看起来问题是您在尝试捕获保存的值时尝试使用尚未设置的值。

修复它所需要做的就是使用您定义的字符串常量。

因此，在 中onCreate()，您将拥有：

if(savedInstanceState!=null){
    mCreate=savedInstanceState.getInt(CREATE_KEY);
    mRestart=savedInstanceState.getInt(RESTART_KEY);
    mResume=savedInstanceState.getInt(RESUME_KEY);
    mStart=savedInstanceState.getInt(START_KEY);
}

然后，在 中onSaveInstanceState()，您将拥有：

savedInstanceState.putInt(CREATE_KEY,mCreate);
savedInstanceState.putInt(RESTART_KEY,mRestart);
savedInstanceState.putInt(RESUME_KEY,mResume);
savedInstanceState.putInt(START_KEY,mStart);
于 2015-05-23T18:52:15.457 回答