java - 我在有意发送整数数据时遇到一些麻烦。 (安卓)

Question

我正在尝试使用 Intent 将整数数据从一个 Activity 发送到另一个类，但我的整数数据只是自行变为零。

所以我做了这个 Intent ，将有关用户想要执行多少时间间隔的数据发送到一个类，该类根据用户为回收器 View 选择的数量来创建 View 组/ View 持有者。问题是 int 本身会自动变成零，这导致回收者列表没有被创建。我尝试使用随机数创建列表，并且它有效，因此这部分代码没有任何问题。

另外，经过一些调试后，我将问题范围缩小到了 getintent 部分，因为在发送数据之前，数字是正确的，但在发送数据之后，数字总是变成零。

public class MainActivity extends AppCompatActivity {
    Button decrementButton;
    TextView intervalCountTextView;
    Button incrementButton;
    int intervalCount = 0;
    Button intervalButtonSetter;
    private int numberOfIntervals = 0;
    private static final String TAG = "MainActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);



        decrementButton = findViewById(R.id.decrementButton);
        intervalCountTextView = findViewById(R.id.intervallCount);
        incrementButton = findViewById(R.id.incrementButton);
        intervalButtonSetter = findViewById(R.id.intervalButtonSetter);

        decrementButton.setVisibility(View.INVISIBLE);

        decrementButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                intervalCount--;
                intervalCountSetter();

            }
        });

        // make sure you can't decrement past zero

        incrementButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                intervalCount++;
                intervalCountSetter();
            }
        });

        intervalButtonSetter.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                sendDataToAdapter();
            }
        });
    }



    private void intervalCountSetter() {
        String intervalCountString = Integer.toString(intervalCount);
        intervalCountTextView.setText(intervalCountString);

        if (intervalCount > 0) {
            decrementButton.setVisibility(View.VISIBLE);
        } else {
            decrementButton.setVisibility(View.INVISIBLE);
        }
    }

    private void sendDataToAdapter() {
        String numberOfIntervalsString = intervalCountTextView.getText().toString();
        numberOfIntervals= Integer.parseInt(numberOfIntervalsString);
        setNumberOfIntervals(numberOfIntervals);
        if (numberOfIntervals > 0) {
            Log.d(TAG, "sendDataToAdapter: We have the numbers");
            Log.d(TAG, "sendDataToAdapter: " + numberOfIntervals);
          startTimeActivity();

        } else {
            Toast.makeText(this, "You have to have at least 1 interval.", Toast.LENGTH_LONG).show();
        }

    }

    private void startTimeActivity() {
        startActivity(new Intent(this, TimeActivity.class));
        Log.d(TAG, "startTimeActivity: TimeActivity has been started" + numberOfIntervals);


    }

    public int getNumberOfIntervals() {
        return numberOfIntervals;
    }

    public void setNumberOfIntervals(int numberOfIntervals) {
        this.numberOfIntervals = numberOfIntervals;
    }
}

public class TimeActivity extends AppCompatActivity {

    public static final String TAG = TimeActivity.class.getSimpleName();
    private MainActivity mainActivityObject = new MainActivity();
    private int numberOfIntervals = mainActivityObject.getNumberOfIntervals();
    private ArrayList<Integer> WTV = new ArrayList<>();
    private ArrayList<Integer> WET = new ArrayList<>();
    private ArrayList<Integer> RTV = new ArrayList<>();
    private ArrayList<Integer> RET = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_time);
        Log.d(TAG, "onCreate: Started");



        Toast.makeText(this, "" + numberOfIntervals, Toast.LENGTH_LONG).show();


        //Intent intent = getIntent();
        //numberOfIntervals = intent.getIntExtra("Interval Count", 0);
        //Log.d(TAG, "" + numberOfIntervals);

        initializeViews();






    }

    private void initializeViews() {
        Log.d(TAG, "initializeViews: Preparing views");
        //Make sure they can change through the R.strings


        WTV.add(R.string.work_text_view);
        WET.add(R.string.default_time_value);
        RTV.add(R.string.rest_text_view);
        RET.add(R.string.default_time_value);

        initializeRecyclerView();
    }

    private void initializeRecyclerView() {
        Log.d(TAG, "initializeRecyclerView: Initialize RecyclerView");
        RecyclerView intervalRecyclerView = findViewById(R.id.intervalRecyclerView);
        CustomAdapter adapter = new CustomAdapter(this, WTV, WET, RTV, RET);
        intervalRecyclerView.setAdapter(adapter);
        intervalRecyclerView.setLayoutManager(new LinearLayoutManager(this));

    }
}

 private static final String TAG = "CustomAdapter";

    private ArrayList<Integer> mWorkTW = new ArrayList<>();
    private ArrayList<Integer> mWorkET = new ArrayList<>();
    private ArrayList<Integer> mRestTW = new ArrayList<>();
    private ArrayList<Integer> mRestET = new ArrayList<>();
    private Context mContext;
    private MainActivity mainActivityObject = new MainActivity();
    private int numberOfIntervals = mainActivityObject.getNumberOfIntervals();








    public CustomAdapter( Context context , ArrayList<Integer> mWorkTW, ArrayList<Integer> mWorkET, ArrayList<Integer> mRestTW, ArrayList<Integer> mRestET) {

        this.mWorkTW = mWorkTW;
        this.mWorkET = mWorkET;
        this.mRestTW = mRestTW;
        this.mRestET = mRestET;
        this.mContext = context;
        Log.d(TAG, "CustomAdapter: " + numberOfIntervals);
    }





    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View customView = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.time_row, viewGroup,false);
        ViewHolder holder = new ViewHolder(customView);
        return holder;

    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder viewHolder, int i) {
        Log.d(TAG, "onBindViewHolder: called");
        viewHolder.workTextView.setText(R.string.work_text_view);
        viewHolder.restTextView.setText(R.string.rest_text_view);
        viewHolder.workEditText.setHint(R.string.default_time_value);
        viewHolder.restEditText.setHint(R.string.default_time_value);
    }

    @Override
    public int getItemCount() {
        Log.d(TAG, "" + numberOfIntervals);
        return numberOfIntervals;
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        TextView workTextView;
        EditText workEditText;
        TextView restTextView;
        EditText restEditText;
        ConstraintLayout parentLayout;


        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            workTextView = itemView.findViewById(R.id.workTextView);
            workEditText = itemView.findViewById(R.id.workEditText);
            restTextView = itemView.findViewById(R.id.restTextView);
            restEditText = itemView.findViewById(R.id.restEditText);
            parentLayout = itemView.findViewById(R.id.parentLayout);



        }
    }







}

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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=".MainActivity">

    <TextView
        android:id="@+id/intervallCount"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="0"
        android:textSize="24sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.533" />

    <Button
        android:id="@+id/decrementButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        android:text="-"
        android:textSize="30sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/intervallCount"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:text="-" />

    <Button
        android:id="@+id/incrementButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        android:text="+"
        android:textSize="30sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/intervallCount"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/intervalButtonSetter"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:layout_marginBottom="8dp"
        android:text="Set intervall"
        android:textSize="18sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/intervallCount" />

</android.support.constraint.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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=".TimeActivity">

    <android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/intervalRecyclerView">

    </android.support.v7.widget.RecyclerView>


</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    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"
    android:id="@+id/parentLayout">

    <TextView
        android:id="@+id/workTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="@string/work_text_view"
        android:textSize="24sp"
        tools:layout_editor_absoluteX="31dp"
        tools:layout_editor_absoluteY="8dp" />

    <EditText
        android:id="@+id/workEditText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_weight="1"
        android:ems="10"
        android:hint="@string/default_time_value"
        android:inputType="number"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/restTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_weight="1"
        android:text="@string/rest_text_view"
        android:textSize="24sp"
        app:layout_constraintEnd_toStartOf="@+id/restEditText"
        app:layout_constraintHorizontal_bias="0.425"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/workEditText" />

    <EditText
        android:id="@+id/restEditText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_weight="1"
        android:ems="10"
        android:hint="@string/default_time_value"
        android:inputType="number"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/workEditText" />


</android.support.constraint.ConstraintLayout>

我希望从 Activity 发送到类的 int 是相同的，并且不会自动更改为零

Answer 1

目前，您有一个 Intent 作为 sendDataToAdapter() 中的局部变量，它获取额外的间隔数。由于您没有对此 Intent 执行任何其他操作，因此一旦该方法完成，它将被垃圾回收，额外的内容将无法从该方法之外的任何地方访问。

在 startTimeActivity() 中，您实例化一个新的 Intent 来启动 TimeActivity。此Intent没有任何额外内容。但这是 Intent，其额外内容将传递给 TimeActivity。

因此，为了将间隔数作为正确的 Intent 的额外内容，您可以向 startTimeActivity() 添加参数 numberOfIntervals(请注意，我使用字符串常量以避免因拼写错误引起的错误)

public static final String INTERVAL_COUNT = "INTERVAL_COUNT";

private void startTimeActivity(int numberOfIntervals) {
    Intent intent = new Intent(this, TimeActivity.class);
    intent.putExtra(INTERVAL_COUNT, numberOfIntervals)
    startActivity(intent);
    Log.d(TAG, "startTimeActivity: TimeActivity has been started" + numberOfIntervals);
}

由于您需要知道CustomAdapter中的间隔数量，因此可以在构造函数中添加另一个参数:

public CustomAdapter(Context context, ArrayList<Integer> mWorkTW, ArrayList<Integer> mWorkET, ArrayList<Integer> mRestTW, ArrayList<Integer> mRestET, int numberOfIntervals) {
    this.mWorkTW = mWorkTW;
    // ...
    this.numberOfIntervals = numberOfIntervals;
    Log.d(TAG, "CustomAdapter: " + numberOfIntervals);
}

在TimeActivity中，您可以通过调用getIntent()来访问int值:

private int numberOfIntervals;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_time);
    Log.d(TAG, "onCreate: Started");
    numberOfIntervals = getIntent().getIntExtra(INTERVAL_COUNT, 0);
    Toast.makeText(this, "" + numberOfIntervals, Toast.LENGTH_LONG).show();
    Log.d(TAG, "" + numberOfIntervals);
    initializeViews();
}

最后，您可以在 TimeActivity 中初始化 RecyclerView，如下所示:

private void initializeRecyclerView() {
    Log.d(TAG, "initializeRecyclerView: Initialize RecyclerView");
    RecyclerView intervalRecyclerView = findViewById(R.id.intervalRecyclerView);
    CustomAdapter adapter = new CustomAdapter(this, WTV, WET, RTV, RET, numberOfIntervals);
    intervalRecyclerView.setAdapter(adapter);
    intervalRecyclerView.setLayoutManager(new LinearLayoutManager(this));
}