Question

我的源代码如下：

这是ActiviyOne.java

package course.labs.activitylab;

        import android.app.Activity;
        import android.app.Fragment;
        import android.content.Intent;
        import android.os.Bundle;
        import android.util.Log;
        import android.view.View;
        import android.view.View.OnClickListener;
        import android.widget.Button;
        import android.widget.TextView;

public class ActivityOne
        extends Activity {

    // Use these as keys when you're saving state between reconfigurations
    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";

    // String for LogCat documentation
    private final static String TAG = "Lab-ActivityOne";

    // Lifecycle counters
    // TODO:
    public Integer mCreate = 0;
    public Integer mRestart = 0;
    public Integer mStart = 0;
    public Integer mResume = 0;
    // Create variables named
    // mCreate, mRestart, mStart and mResume
    // to count calls to onCreate(), onRestart(), onStart() and
    // onResume(). These variables should not be defined as static.
    // You will need to increment these variables' values when their
    // corresponding lifecycle methods get called.
    // TODO: Create variables for each of the TextViews
    TextView mTvCreate;
    TextView mTvRestart;
    TextView mTvStart;
    TextView mTvResume;

    // named mTvCreate, mTvRestart, mTvStart, mTvResume.
    // for displaying the current count of each counter variable
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_one);

        // TODO: Assign the appropriate TextViews to the TextView variables
        mTvCreate = (TextView) findViewById(R.id.create);
        mTvRestart = (TextView) findViewById(R.id.restart);
        mTvResume = (TextView) findViewById(R.id.resume);
        mTvStart = (TextView) findViewById(R.id.start);
        // Hint: Access the TextView by calling Activity's findViewById()
        // textView1 = (TextView) findViewById(R.id.textView1);

        Button launchActivityTwoButton = (Button) findViewById(R.id.bLaunchActivityTwo);
        launchActivityTwoButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO:
                // Launch Activity Two
                // Hint: use Context's startActivity() method
                // Create an intent stating which Activity you would like to
                // start
                //Intent intent = null;
                Intent StartIntent = new Intent(getApplicationContext(), ActivityTwo.class);
                startActivity(StartIntent);
                // Launch the Activity using the intent
            }
        });

        // Has previous state been saved?
        if(savedInstanceState != null) {
            // TODO:
            // Restore value of counters from saved state
            // Only need 4 lines of code, one for every count variable
            mCreate = savedInstanceState.getInt(CREATE_KEY);
            mStart = savedInstanceState.getInt(START_KEY);
            mRestart = savedInstanceState.getInt(RESTART_KEY);
            mResume = savedInstanceState.getInt(RESUME_KEY);
            //Log.i(TAG, "mCreate " + mCreate + "mResume " + mResume + "mStart " + mStart + "mRestart " + mRestart);
            //super.onSaveInstanceState(savedInstanceState);
        }

        // Emit LogCat message
        Log.i(TAG, "Entered the onCreate() method");
        // TODO:
        mCreate++;
        displayCounts();
        // Update the appropriate count variable
        // Update the user interface via the displayCounts() method
    }

    // Lifecycle callback overrides

    @Override
    public void onStart() {
        super.onStart();
        // Emit LogCat message
        Log.i(TAG, "Entered the onStart() method");
        // TODO:
        mStart++;
        displayCounts();
        // Update the appropriate count variable
        // Update the user interface
    }

    @Override
    public void onResume() {
        super.onResume();
        // Emit LogCat message
        Log.i(TAG, "Entered the onResume() method");
        // TODO:
        mResume++;
        displayCounts();
        // Update the appropriate count variable
        // Update the user interface
    }

    @Override
    public void onPause() {
        super.onPause();
        // Emit LogCat message
        Log.i(TAG, "Entered the onPause() method");
    }

    @Override
    public void onStop() {
        super.onStop();
        // Emit LogCat message
        Log.i(TAG, "Entered the onStop() method");
    }

    @Override
    public void onRestart() {
        super.onRestart();
        // Emit LogCat message
        Log.i(TAG, "Entered the onRestart() method");
        // TODO:
        mRestart++;
        displayCounts();
        // Update the appropriate count variable
        // Update the user interface
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        // Emit LogCat message
        Log.i(TAG, "Entered the onDestroy() method");
    }

    @Override
    public void onSaveInstanceState(Bundle savedInstanceState) {
        // TODO:
        super.onSaveInstanceState(savedInstanceState);
        savedInstanceState.putInt(CREATE_KEY, mCreate);
        savedInstanceState.putInt(RESTART_KEY, mRestart);
        savedInstanceState.putInt(RESUME_KEY, mResume);
        savedInstanceState.putInt(START_KEY, mStart);
        // Save state information with a collection of key-value pairs
        // 4 lines of code, one for every count variable
    }

    // Updates the displayed counters
    // This method expects that the counters and TextView variables use the
    // names
    // specified above
    public void displayCounts() {
        // TODO - uncomment these lines
        mTvCreate.setText("onCreate() calls: " + mCreate);
        mTvStart.setText("onStart() calls: " + mStart);
        mTvResume.setText("onResume() calls: " + mResume);
        mTvRestart.setText("onRestart() calls: " + mRestart);
    }
}

这是ActivityTwo.java

    package course.labs.activitylab;

    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.TextView;

public class ActivityTwo
        extends Activity {

    // Use these as keys when you're saving state between reconfigurations
    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";

    // String for LogCat documentation
    private final static String TAG = "Lab-ActivityTwo";

    // Lifecycle counters
    // TODO:
    public Integer mCreate = 0;
    public Integer mRestart = 0;
    public Integer mStart = 0;
    public Integer mResume = 0;

    // Create variables named   
    // mCreate, mRestart, mStart and mResume    
    // to count calls to onCreate(), onRestart(), onStart() and
    // onResume(). These variables should not be defined as static.
    // You will need to increment these variables' values when their
    // corresponding lifecycle methods get called.
    // TODO: Create variables for each of the TextViews
    TextView mTvCreate;
    TextView mTvRestart;
    TextView mTvStart;
    TextView mTvResume;
    // named  mTvCreate, mTvRestart, mTvStart, mTvResume.
    // for displaying the current count of each counter variable
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_two);
        // TODO: Assign the appropriate TextViews to the TextView variables
        mTvCreate = (TextView) findViewById(R.id.create);
        mTvRestart = (TextView) findViewById(R.id.restart);
        mTvStart = (TextView) findViewById(R.id.start);
        mTvResume = (TextView) findViewById(R.id.resume);
        // Hint: Access the TextView by calling Activity's findViewById()
        // textView1 = (TextView) findViewById(R.id.textView1);
        Button closeButton = (Button) findViewById(R.id.bClose);
        closeButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO:
                    /*
                    Intent FinishIntent = new Intent(ActivityTwo.this, ActivityOne.class);
                    finish();
                    */
                // This function closes Activity Two
                // Hint: use Context's finish() method
                // ActivityTwo.this.finish();
                // finish();
                //  Intent tmpIntent = new Intent(getApplicationContext(), ActivityOne.class);
                finish();
                //ActivityTwo.this.finish();
            }
        });
    /*
            savedInstanceState.putInt(CREATE_KEY, mCreate);
            savedInstanceState.putInt(RESTART_KEY, mRestart);
            savedInstanceState.putInt(RESUME_KEY, mResume);
            savedInstanceState.putInt(START_KEY, mStart);
    */
        // Has previous state been saved?
        if(savedInstanceState != null) {
            // TODO:
            // Log.i(TAG, "Entered restoring values of counters");
            super.onRestoreInstanceState(savedInstanceState);
            mCreate = savedInstanceState.getInt(CREATE_KEY);
            mStart = savedInstanceState.getInt(START_KEY);
            mRestart = savedInstanceState.getInt(RESTART_KEY);
            mResume = savedInstanceState.getInt(RESUME_KEY);
            //Log.i(TAG, "mCreate " + mCreate + "mResume " + mResume + "mStart " + mStart + "mRestart " + mRestart);
            // Restore value of counters from saved state
            // Only need 4 lines of code, one for every count variable
            // super.onSaveInstanceState(savedInstanceState);
        }
        // Emit LogCat message
        mCreate++;
        Log.i(TAG, "Entered the onCreate() method");
        // TODO:
        displayCounts();
        // Update the appropriate count variable
        // Update the user interface via the displayCounts() method
    }

    // Lifecycle callback methods overrides

    @Override
    public void onStart() {
        super.onStart();
        // Emit LogCat message
        mStart++;
        Log.i(TAG, "Entered the onStart() method");
        // TODO:
        displayCounts();
        // Update the appropriate count variable
        // Update the user interface
    }

    @Override
    public void onResume() {
        super.onResume();
        // Emit LogCat message
        mResume++;
        Log.i(TAG, "Entered the onResume() method");
        // TODO:
        displayCounts();
        // Update the appropriate count variable
        // Update the user interface
    }

    @Override
    public void onPause() {
        super.onPause();
        // Emit LogCat message
        Log.i(TAG, "Entered the onPause() method");
    }

    @Override
    public void onStop() {
        super.onStop();
        // Emit LogCat message
        Log.i(TAG, "Entered the onStop() method");
    }

    @Override
    public void onRestart() {
        super.onRestart();
        // Emit LogCat message
        mRestart++;
        Log.i(TAG, "Entered the onRestart() method");
        // TODO:
        displayCounts();
        // Update the appropriate count variable
        // Update the user interface
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        // Emit LogCat message
        Log.i(TAG, "Entered the onDestroy() method");
    }

    @Override
    public void onSaveInstanceState(Bundle savedInstanceState) {
        // TODO:
        // Save counter state information with a collection of key-value pairs
        // 4 lines of code, one for every count variable
        Log.i(TAG, "Saving instance state");
        super.onSaveInstanceState(savedInstanceState);
        savedInstanceState.putInt(CREATE_KEY, mCreate);
        savedInstanceState.putInt(RESTART_KEY, mRestart);
        savedInstanceState.putInt(RESUME_KEY, mResume);
        savedInstanceState.putInt(START_KEY, mStart);
    }

    // Updates the displayed counters
    // This method expects that the counters and TextView variables use the
    // names
    // specified above
    public void displayCounts() {
        // TODO - uncomment these lines
        mTvCreate.setText("onCreate() calls: " + mCreate);
        mTvStart.setText("onStart() calls: " + mStart);
        mTvResume.setText("onResume() calls: " + mResume);
        mTvRestart.setText("onRestart() calls: " + mRestart);
    }
}

我有问题。当我运行该程序时，我想要计算我调用的次数

onCreate()，onStart()，onResume()，onResume()适用于活动一，但不适用于活动2.计数器不工作。

由于

Answer 1

1）Activity1状态保存在堆栈上 - ＆gt;当你打电话给Activity2时。

2）单击后退Activity2状态被保存然后销毁（从堆栈中删除）。

3）Activity1从堆栈中读取已保存的状态。

试试这[活动1]：

 launchActivityTwoButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                    Intent StartIntent = new Intent(getApplicationContext(), ActivityTwo.class);
    StartIntent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
    startActivity(StartIntent);
            }
        });

[活动2]：

 closeButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
               Intent intent= new Intent(getApplicationContext(), ActivityOne.class);
intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivity(intent);
            }
        });

Answer 2

您已将计数器创建为局部变量。

public Integer mCreate = 0;
public Integer mRestart = 0;
public Integer mStart = 0;
public Integer mResume = 0;

因此，在Activity2被销毁之后，即在调用onStop（）之后，这些变量也会被删除。

解决方案：创建一个新类并在其中创建静态计数器变量。

Answer 3

        super.onRestoreInstanceState(savedInstanceState);

您不应在onCreate()中调用此方法。

对于启动ActivityOne.this的{{1}}，您还应该使用getApplicationContext()代替Intent。

ActivityTwo.java没有计算

3 个答案: