Question

对于每个回调事件（onCreate（），onStart（）...），记录在日志中触发的回调事件（使用Log.d）;应该在“strings.xml”中定义写入日志的消息，并使用getResources.getString（）来检索消息

实现onSaveInstanceState和onRestoreInstanceState - 跟踪onSaveInstanceState被调用的次数，在onRestoreInstanceState中，将值打印到日志文件

“Log”语句的标签也应该在strings.xml中定义并使用getResources.getString（）

进行设置

package com.csci235labs.rob_lifecycles;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

public class MainActivity extends AppCompatActivity {

String TAG = getResources().getString(R.string.app_name); //Logcat tag
String ActivityState;
int instanceTimes; //number of times instance is called
String Act_keys;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    //recover instance state
    if(savedInstanceState!=null)
    {
        ActivityState = savedInstanceState.getString(Act_keys);
    }
    else
    {
        instanceTimes=0;
        Act_keys="";
    }

    setContentView(R.layout.activity_main);


}

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    instanceTimes++;
    ActivityState=String.valueOf(instanceTimes);

    outState.putString(Act_keys,ActivityState);

    super.onSaveInstanceState(outState);
}


@Override
protected void onStart() {
    super.onStart();
    //logs event message
    String eventMessage=getResources().getString(R.string.on_start_str);
    Log.d(TAG,eventMessage);
}

@Override
protected void onResume() {
    super.onResume();
    //logs event message
    String eventMessage=getResources().getString(R.string.on_resume_str);
    Log.d(TAG,eventMessage);
}

@Override
protected void onPause() {
    super.onPause();
    //logs event message
    String eventMessage=getResources().getString(R.string.on_pause_str);
    Log.d(TAG,eventMessage);
}

@Override
protected void onStop() {
    super.onStop();
    //logs event message
    String eventMessage=getResources().getString(R.string.on_stop_str);
    Log.d(TAG,eventMessage);
}

@Override
protected void onDestroy() {
    super.onDestroy();
    //logs event message
    String eventMessage=getResources().getString(R.string.on_destroy_str);
    Log.d(TAG,eventMessage);
 }
}

XML文件：

<resources>
  <string name="app_name">rob_lifecycles</string>
  <string name="app_str">teststring</string>
  <string name="on_create_str">onCreate() method</string>
  <string name="on_start_str">onStart() method</string>
  <string name="on_resume_str">onResume() method</string>
  <string name="on_pause_str">onPause() method</string>
  <string name="on_stop_str">onStop() method</string>
  <string name="on_destroy_str">onDestroy() method</string>
  <string name="action_settings">Settings</string>
</resources>

Answer 1

删除外部的TAG初始化并将其移动到onCreate（），因为在这种情况下context.getResources（）将给出空指针异常

public class MainActivity extends AppCompatActivity {

String TAG;
String ActivityState;
int instanceTimes; //number of times instance is called
String Act_keys;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);


    setContentView(R.layout.activity_main);
    TAG = getResources().getString(R.string.app_name); //Logcat tag
    //recover instance state
    if(savedInstanceState!=null)
    {
       ActivityState = savedInstanceState.getString(Act_keys);
    }
    else
    {
       instanceTimes=0;
       Act_keys="";
    }
}

我的生命周期代码没有编译

1 个答案: