java - OnCretae() 不算数

Question

我一直在 android Studio 中研究这两个方法，当我返回到未添加 OnCreate 方法的 ActivityOne 时，问题就出现了，而如果它添加了 OnStart、OnResume 和 OnRestart，则会出现问题。

Activity 一

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
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 AppCompatActivity {

    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:
    // Create counter variables for onCreate(), onRestart(), onStart() and
    // onResume(), called mCreate, etc.
    // You will need to increment these variables' values when their
    // corresponding lifecycle methods get called
    int mCreate = 0;
    int mRestart = 0;
    int mStart = 0;
    int mResume = 0;

    // TODO: Create variables for each of the TextViews, called
    // mTvCreate, etc.
    TextView mTvCreate;
    TextView mTvStart;
    TextView mTvResume;
    TextView mTvRestart;

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

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

        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 = new Intent(ActivityOne.this, ActivityTwo.class);

                // Launch the Activity using the intent
                startActivity(intent);
            }
        });

        // Check for previously saved state
        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);
            mRestart = savedInstanceState.getInt(RESTART_KEY);
            mStart = savedInstanceState.getInt(START_KEY);
            mResume = savedInstanceState.getInt(RESUME_KEY);
        }

        // Update the appropriate count variable
        mCreate++;

        // TODO: Emit LogCat message
        Log.i(TAG, "Entered the onCreate() method");


        // TODO:
        // Update the user interface via the displayCounts() method
        displayCounts();
    }

    // Lifecycle callback overrides

    @Override
    public void onStart() {
        super.onStart();

        // Update the appropriate count variable
        mStart++;

        // TODO: Emit LogCat message
        Log.i(TAG, "Entered the onStart() method");

        // TODO:
        // Update the user interface
        displayCounts();

    }

    @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);
    }
}

Activity 二

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.view.menu.ActionMenuItemView;
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

    Button closeButton;

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

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

        closeButton = (Button)findViewById(R.id.bClose);

        closeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                finish();
            }
        });
        // Check for previously saved state
        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);
            mRestart = savedInstanceState.getInt(RESTART_KEY);
            mStart = savedInstanceState.getInt(START_KEY);
            mResume = savedInstanceState.getInt(RESUME_KEY);
        }

        // Update the appropriate count variable
        mCreate++;

        // TODO: Emit LogCat message
        Log.i(TAG, "Entered the onCreate() method");

        // TODO:
        // Update the user interface via the displayCounts() method
        displayCounts();
    }

    // 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);
    }
}

Answer 1

when I return to the ActivityOne that does not add to the OnCreate method

因为当你从ActivityTwo返回时android生命周期没有调用它

检查此生命周期