如果存在，则在Onpause（）中的共享preferences访问 - 应用程序崩溃

Question

我正在进行一个学校项目，因此，具体来说，需要从Onpause方法中保存共享的偏好，然后在onCreate方法中调用，并在EditText的值中放置在EssharePreferences中的价值中。活动中的两个“ button_dont”中的按钮应该只带您回到活动中，但是现在我添加了它不断关闭应用程序的Onpause方法。

最重要的是，我不明白如何从使用的仿真器中访问ADB。我尝试从Android Studio中找到DeviceManager中的文件，但在数据文件中找不到我的项目名称。我是新手。接下来我可以尝试什么？

<?xml version="1.0" encoding="utf-8"?>
    <GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_row="4"
        android:layout_column="3"
        android:layout_weight="1"
        android:layout_gravity="fill"
        >
    
        <TextView
            android:id="@+id/textView"
            android:layout_width="256dp"
            android:layout_height="66dp"
            android:layout_row="0"
            android:layout_column="0"
            android:text="@string/enterName"
            android:textSize="30sp" />
    
        <EditText
            android:id="@+id/editText"
            android:layout_width="441dp"
            android:layout_height="wrap_content"
            android:layout_row="1"
            android:layout_column="0"
            android:layout_columnSpan="2"
            android:textSize="40sp"/>
    
        <Button
            android:id="@+id/next"
            android:layout_width="127dp"
            android:layout_height="64dp"
            android:layout_row="2"
            android:layout_column="0"
            android:text="@string/next" />
    </GridLayout>


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".NameActivity"
    android:orientation="vertical">


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:id="@+id/welcome"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/welcome"
            android:textSize="30sp" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="416dp"
        android:layout_height="87dp"
        android:orientation="horizontal">

        <Button
            android:id="@+id/button_dont"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/dont_call"
            android:layout_margin="5sp"
            />

        <Button
            android:id="@+id/button_do"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/thank_you"
            android:layout_margin="5sp"/>
    </LinearLayout>

</LinearLayout>

代码：

public class NameActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_name);

        TextView welcome = findViewById(R.id.welcome);

        Intent i = getIntent();
        String name = i.getStringExtra("Value");
        welcome.setText("Welcome "+ name +"!");

        Button button_dont = findViewById(R.id.button_dont);
        Button button_do = findViewById(R.id.button_do);

        button_dont.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i = new Intent();
                i.putExtra("result",0);

                setResult(Activity.RESULT_OK,i);
                finish();
            }
        });
    
            button_do.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Intent i = new Intent();
                    i.putExtra("result",1);
                    setResult(RESULT_OK, i);
                    finish();
                }
            });
        }
    }

public class MainActivity extends AppCompatActivity {
    Button next;
    EditText editText;
    public static final int REQ_CODE=1014;

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

        Button next = findViewById(R.id.next);
        EditText editText = findViewById(R.id.editText);

        next.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i = new Intent(getApplicationContext(),NameActivity.class);
                String name = editText.getText().toString();
                i.putExtra("Value",name);
                startActivityForResult(i,1014);
            }
        });
    }

    @Override
    protected void onPause() {
        super.onPause();
        SharedPreferences sharedPrefs = getSharedPreferences("Names", Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPrefs.edit();
        editor.putString("name", editText.getText().toString());
        editor.commit();
    }

    @Override
    public void onActivityResult (int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        int result = data.getIntExtra("result", 2);

        if (result == 1) {
          finish();
        }
    }}

Answer 1

您不能在Onpause中创建并在OnCreate上访问，只能在创建和初始化onCreate的外部创建，然后在其他功能中使用。

为此，您需要在ongreate中初始化该功能，然后您可以在其他地方使用。
像这样

public class MainActivity extends AppCompatActivity {
    Button next;
    EditText editText;
    public static final int REQ_CODE=1014;
    SharedPreferences sharedPrefs;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 sharedPrefs = getSharedPreferences("Names", Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPrefs.edit();
        editor.putString("name", editText.getText().toString());
        editor.commit();

        Button next = findViewById(R.id.next);
        EditText editText = findViewById(R.id.editText);

        next.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i = new Intent(getApplicationContext(),NameActivity.class);
                String name = editText.getText().toString();
                i.putExtra("Value",name);
                startActivityForResult(i,1014);
            }
        });
    }

    @Override
    protected void onPause() {
        super.onPause();
       
    }

    @Override
    public void onActivityResult (int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        int result = data.getIntExtra("result", 2);

        if (result == 1) {
          finish();
        }
    }}````

So when u do it like this, u can call and use it anywhere in the class