java - 切换内容 View 时信息不会保存

Question

我是 Android 开发新手，正在尝试制作一个简单的应用程序来记录篮球比赛的得分和球队阵容。问题是，每当我在 View 之间来回切换时，得分(或阵容)都会显示为默认设置为零(或没有球员)。我添加了代码(我尽可能地格式化了它)，但我相信，因为这可能是一个逻辑错误，所以唯一重要的部分是顶部的 MainActivity 类。感谢您的帮助!

package com.example.ryan.basketballscorekeeper;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    homeScore=0;
    awayScore=0;
}

int homeScore;
int awayScore;


public void lineupsView(View view){
    TextView textView = (TextView) findViewById(R.id.homeTeamScore);
    textView.setText(homeScore+"");
    TextView textView2 = (TextView) findViewById(R.id.awayTeamScore);
    textView.setText(awayScore+"");
    setContentView(R.layout.lineups);
}
public void mainView(View view){

    EditText editText1 = (EditText) findViewById(R.id.one);
    editText1.setText(editText1.getText());
    EditText editText2 = (EditText) findViewById(R.id.two);
    editText2.setText(editText2.getText());
    EditText editText3 = (EditText) findViewById(R.id.three);
    editText3.setText(editText3.getText());
    EditText editText4 = (EditText) findViewById(R.id.four);
    editText4.setText(editText4.getText());
    EditText editText5 = (EditText) findViewById(R.id.five);
    editText5.setText(editText5.getText());
    setContentView(R.layout.activity_main);
}


public void threePointerAway(View view){
    TextView textView = (TextView) findViewById(R.id.awayTeamScore);
    awayScore+=3;
    textView.setText(awayScore+"");
}
public void threePointerHome(View view){
    TextView textView = (TextView) findViewById(R.id.homeTeamScore);
    homeScore+=3;
    textView.setText(homeScore+"");
}
public void twoPointerHome(View view){
    TextView textView = (TextView) findViewById(R.id.homeTeamScore);
    homeScore+=2;
    textView.setText(homeScore+"");
}
public void twoPointerAway(View view){
    TextView textView = (TextView) findViewById(R.id.awayTeamScore);
    awayScore+=2;
    textView.setText(awayScore+"");
}
public void freeThrowHome(View view){
    TextView textView = (TextView) findViewById(R.id.homeTeamScore);
    homeScore+=1;
    textView.setText(homeScore+"");
}
public void freeThrowAway(View view){
    TextView textView = (TextView) findViewById(R.id.awayTeamScore);
    awayScore+=1;
    textView.setText(awayScore+"");
}

public void reset(View view){
    TextView awayView = (TextView) findViewById(R.id.awayTeamScore);
    TextView homeView = (TextView) findViewById(R.id.homeTeamScore);
    homeScore=0;
    awayScore=0;
    awayView.setText(awayScore + "");
    homeView.setText(homeScore + "");
}


}

//////////////.java 文件结束//////////////////////////////////

//////////////计分 View 开始////////////////////////////

<ImageView
    android:layout_width="match_parent"
   android:layout_height="match_parent"
    android:src="@drawable/bballcourt"
    android:scaleType="centerCrop"
    />


<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    >
    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:layout_gravity="center"
        android:orientation="vertical"
        >

        <TextView
            android:textColor="#ffffff"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Home Team"
            android:layout_margin="10dp"
            android:layout_gravity="center"
            android:textSize="15dp"
            />
        <TextView
            android:textColor="#ffffff"
            android:id="@+id/homeTeamScore"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="0"
            android:textSize="50dp"
            android:layout_gravity="center"
            />
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="+3 Points"
            android:background="#ffbf80"
            android:layout_gravity="center"
            android:onClick="threePointerHome"
            android:layout_marginTop="20dp"
            android:textSize="20dp"
            android:padding="10dp"
            />
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="+2 Points"
            android:background="#ffbf80"
            android:layout_gravity="center"
            android:onClick="twoPointerHome"
            android:layout_marginTop="20dp"
            android:textSize="20dp"
            android:padding="10dp"
            />
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Free Throw"
            android:background="#ffbf80"
            android:layout_gravity="center"
            android:onClick="freeThrowHome"
            android:layout_marginTop="20dp"
            android:textSize="17dp"
            android:padding="10dp"
            />
    </LinearLayout>

    <View
        android:layout_width="5dp"
        android:layout_height="340dp"
        android:background="#d9d9d9"
        android:layout_marginTop="40dp"

        />

    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:layout_gravity="center"
        android:orientation="vertical"
        >

        <TextView
            android:textColor="#ffffff"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Away Team"
            android:layout_margin="10dp"
            android:layout_gravity="center"
            android:textSize="15dp"
            />
        <TextView
            android:textColor="#ffffff"
            android:id="@+id/awayTeamScore"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="0"
            android:textSize="50dp"
            android:layout_gravity="center"
            />
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="+3 Points"
            android:background="#ffbf80"
            android:layout_gravity="center"
            android:onClick="threePointerAway"
            android:layout_marginTop="20dp"
            android:textSize="20dp"
            android:padding="10dp"
            />
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="+2 Points"
            android:background="#ffbf80"
            android:layout_gravity="center"
            android:onClick="twoPointerAway"
            android:layout_marginTop="20dp"
            android:textSize="20dp"
            android:padding="10dp"
            />
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Free Throw"
            android:background="#ffbf80"
            android:layout_gravity="center"
            android:onClick="freeThrowAway"
            android:layout_marginTop="20dp"
            android:textSize="17dp"
            android:padding="10dp"
            />
    </LinearLayout>

</LinearLayout>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="reset"
    android:textAllCaps="true"
    android:layout_centerHorizontal="true"
    android:layout_alignParentBottom="true"
    android:padding="15dp"
    android:layout_marginBottom="40dp"
    android:textSize="20dp"
    android:background="#ffbf80"
    android:onClick="reset"

    />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Lineups"
    android:textAllCaps="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentBottom="true"
    android:padding="15dp"
    android:layout_margin="10dp"
    android:textSize="20dp"
    android:background="#ff8000"
    android:onClick="lineupsView" />

</RelativeLayout>
//////////End Of Scorekeeping View/////////////////////////////////

//////////Beginning of Lineups view/////////////////////////////////
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:src="@drawable/bballcourt"
    android:scaleType="centerCrop"
    />

 <TextView
    android:id="@+id/lineups"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textColor="#ffffff"
    android:text="Lineups"
    android:textSize="30dp"
    android:padding="30dp"
    />

 <EditText
    android:textColor="#ffffff"
    android:id="@+id/one"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="textNoSuggestions"
    android:maxLines="1"
    android:layout_below="@id/lineups"
    />
 <EditText
    android:textColor="#ffffff"
    android:id="@+id/two"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="textNoSuggestions"
    android:maxLines="1"
    android:layout_below="@id/one"
    />
 <EditText
    android:textColor="#ffffff"
    android:id="@+id/three"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="textNoSuggestions"
    android:maxLines="1"
    android:layout_below="@id/two"
    />
 <EditText
    android:textColor="#ffffff"
    android:id="@+id/four"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="textNoSuggestions"
    android:maxLines="1"
    android:layout_below="@id/three"
    />
 <EditText
    android:textColor="#ffffff"
    android:id="@+id/five"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="textNoSuggestions"
    android:maxLines="1"
    android:layout_below="@id/four"
    />
 <Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Score"
    android:textAllCaps="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentBottom="true"
    android:padding="15dp"
    android:layout_margin="10dp"
    android:textSize="20dp"
    android:background="#ff8000"
    android:onClick="mainView"
    />
</RelativeLayout>



</LinearLayout

Answer 1

尝试保存实例的状态，然后在再次显示 Activity 时恢复，覆盖这两个方法:

public void onSaveInstanceState(Bundle savedInstanceState) {}
public void onRestoreInstanceState(Bundle savedInstanceState) {}

因此，当 Activity 恢复时，您可以恢复相应 bundle 中保存的所有数据。

例如:

static final String STATE_SCORE = "playerScore";
static final String STATE_LEVEL = "playerLevel";
...

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
    // Save the user's current game state
    savedInstanceState.putInt(STATE_SCORE, mCurrentScore);
    savedInstanceState.putInt(STATE_LEVEL, mCurrentLevel);

    // Always call the superclass so it can save the view hierarchy state
    super.onSaveInstanceState(savedInstanceState);
}

然后，您可以重写 OnCreate 或 onRestoreInstanceState 来获取旧状态:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState); // Always call the superclass first

    // Check whether we're recreating a previously destroyed instance
    if (savedInstanceState != null) {
        // Restore value of members from saved state
        mCurrentScore = savedInstanceState.getInt(STATE_SCORE);
        mCurrentLevel = savedInstanceState.getInt(STATE_LEVEL);
    } else {
        // Probably initialize members with default values for a new instance
    }
    ...
}  
@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
    // Always call the superclass so it can restore the view hierarchy
    super.onRestoreInstanceState(savedInstanceState);

    // Restore state members from saved instance
    mCurrentScore = savedInstanceState.getInt(STATE_SCORE);
    mCurrentLevel = savedInstanceState.getInt(STATE_LEVEL);
}