如何使用共享首选项添加到收藏夹按钮但在android中没有任何数据库？

Question

我正在使用共享首选项创建切换按钮以添加到收藏夹功能，但是当我单击按钮以添加到收藏夹时它不起作用但是当我移回另一个活动并返回此活动时我的按钮未选中，当我再次点击时，它的说法已从收藏夹中删除，但它应该被标记为收藏，因为我已经将其标记为收藏

XML

<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=".BenefitDescriptionActivity">

    <ToggleButton
        android:id="@+id/favouritetogglebuttonID"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_marginTop="5dp"
        android:layout_marginBottom="5dp"
        android:textOff=""
        android:textOn=""
        app:layout_constraintBottom_toTopOf="@+id/benefitdescriptionscrollviewID"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/benefitimageviewID" />

</android.support.constraint.ConstraintLayout>

Java

import android.content.Context;
import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
import android.widget.ToggleButton;

import static android.text.Html.FROM_HTML_MODE_COMPACT;

public class BenefitDescriptionActivity extends AppCompatActivity {

    private ToggleButton favouriteToggleButton;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_benefit_description);

        favouriteToggleButton = (ToggleButton)findViewById(R.id.favouritetogglebuttonID);
        favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(),R.drawable.ic_favorite_border_black_24dp));
        favouriteToggleButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                boolean isFavourite = readstate();
                if (isFavourite) {                 favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(),R.drawable.ic_favorite_black_24dp));
Toast.makeText(BenefitDescriptionActivity.this,"Added to favorites",Toast.LENGTH_SHORT).show();
                    isFavourite = false;
                    savestate(isFavourite);
                }
                else {
                    favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(),R.drawable.ic_favorite_border_black_24dp));
Toast.makeText(BenefitDescriptionActivity.this,"Removed from favorites",Toast.LENGTH_SHORT).show();
                    isFavourite = true;
                    savestate(isFavourite);
                }
            }
        });

    private void savestate(boolean isFavourite){
        SharedPreferences aSharedPreferences = this.getSharedPreferences("Favourite", Context.MODE_PRIVATE);
        SharedPreferences.Editor aSharedPreferencesEdit = aSharedPreferences.edit();
        aSharedPreferencesEdit.putBoolean("State",isFavourite);
        aSharedPreferencesEdit.apply();
    }
    private boolean readstate(){
        SharedPreferences asharedPreferences = this.getSharedPreferences("Favourite",Context.MODE_PRIVATE);
        return asharedPreferences.getBoolean("State",true);
    }
}

Answer 1

返回活动时，您似乎没有设置存储的值。您需要在onResume 中检查并设置它。还可以像这样更改onClickListener 中的代码：

  favouriteToggleButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    boolean isFavourite = readstate();
                    if (!isFavourite) {                 favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(),R.drawable.ic_favorite_black_24dp));
                        Toast.makeText(BenefitDescriptionActivity.this,"Added to favorites",Toast.LENGTH_SHORT).show();
                        isFavourite = true;
                        savestate(isFavourite);
                    }
                    else {
                        favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(),R.drawable.ic_favorite_border_black_24dp));
                        Toast.makeText(BenefitDescriptionActivity.this,"Removed from favorites",Toast.LENGTH_SHORT).show();
                        isFavourite = false;
                        savestate(isFavourite);
                    }
                }
            });


        }
        private void savestate(boolean isFavourite){
            SharedPreferences aSharedPreferences = this.getSharedPreferences("Favourite", Context.MODE_PRIVATE);
            SharedPreferences.Editor aSharedPreferencesEdit = aSharedPreferences.edit();
            aSharedPreferencesEdit.putBoolean("State",isFavourite);
            aSharedPreferencesEdit.apply();
        }
        private boolean readstate(){
            SharedPreferences asharedPreferences = this.getSharedPreferences("Favourite",Context.MODE_PRIVATE);
            return asharedPreferences.getBoolean("State",false);
        }

        @Override
        protected void onResume() {
            super.onResume();
            boolean isFavourite = readstate();
            Log.e("main","value = " + isFavourite);
            if (!isFavourite) {
                favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(),R.drawable.ic_favorite_border_black_24dp));
            }
            else {
                favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(),R.drawable.ic_favorite_black_24dp));
            }
        }

Answer 2

您总是为您的 favouriteToggleButton 设置一个固定的背景，您需要读取您的 SharedPreferences State 值并为您的 favouriteToggleButton 设置一个背景，只需将这些行添加到您的活动中

  @Override
    protected void onResume() {
        super.onResume();
        if (! readstate()) {
            favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(),R.drawable.ic_favorite_border_black_24dp));
        }
        else {
            favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(),R.drawable.ic_favorite_black_24dp));
        }

Answer 3

尝试设置

    favouriteButton.setChecked(true);   //or false depending

在你的 onClickListener

Answer 4

我在代码中添加了一些注释，这些注释可以帮助您的应用更好地执行。

并且在代码中，您可以将 AsyncTask 替换为其他工具。

只是阻止在 UI 线程中执行 IO 工作。

import android.content.Context;
import android.content.SharedPreferences;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Toast;
import android.widget.ToggleButton;

import java.lang.ref.WeakReference;

public class BenefitDescriptionActivity extends AppCompatActivity {

    private ToggleButton favouriteToggleButton;
    private boolean favourite = false;
    private CheckAsyncTask task;

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

        favouriteToggleButton = (ToggleButton) findViewById(R.id.favouritetogglebuttonID);
        favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.ic_favorite_border_black_24dp));
        favouriteToggleButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                //use a variable, not read file every time click
                if (favourite) {
                    favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.ic_favorite_black_24dp));
                    Toast.makeText(BenefitDescriptionActivity.this, "Added to favorites", Toast.LENGTH_SHORT).show();
                    favourite = false;
                    savestate(favourite);
                } else {
                    favouriteToggleButton.setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.ic_favorite_border_black_24dp));
                    Toast.makeText(BenefitDescriptionActivity.this, "Removed from favorites", Toast.LENGTH_SHORT).show();
                    favourite = true;
                    savestate(favourite);
                }
            }
        });
    }

    @Override
    public void onResume() {
        super.onResume();
        //when activity visible, read boolean value from file and set button state
        if (task == null) {
            task = new CheckAsyncTask(favouriteToggleButton);
        }
        task.execute();
    }

    @Override
    protected void onStop() {
        super.onStop();
        //stop task when activity invisible, prevent memory leak
        if (task != null) {
            task.cancel(true);
        }
    }

    // you also can execute savestate in a background thread
    private void savestate(boolean isFavourite) {
        SharedPreferences aSharedPreferences = getSharedPreferences("Favourite", Context.MODE_PRIVATE);
        SharedPreferences.Editor aSharedPreferencesEdit = aSharedPreferences.edit();
        aSharedPreferencesEdit.putBoolean("State", isFavourite);
        aSharedPreferencesEdit.apply();
    }

    private static class CheckAsyncTask extends AsyncTask<Void, Void, Boolean> {

        private WeakReference<ToggleButton> buttonWeakReference;

        public CheckAsyncTask(ToggleButton button) {
            buttonWeakReference = new WeakReference<>(button);
        }

        @Override
        protected Boolean doInBackground(Void... voids) {
            //do you read file job in background thread may perform better
            if (buttonWeakReference.get() != null) {
                SharedPreferences asharedPreferences = buttonWeakReference.get().getContext().getSharedPreferences("Favourite", Context.MODE_PRIVATE);
                favorite = asharedPreferences.getBoolean("State", true);
                return favorite;
            }

            return false;
        }

        @Override
        protected void onPostExecute(Boolean aBoolean) {
            super.onPostExecute(aBoolean);
            //got read file result set Button state in UI thread
            if (aBoolean && buttonWeakReference != null && buttonWeakReference.get() != null) {
                buttonWeakReference.get().setBackgroundDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.ic_favorite_black_24dp));
            }
        }
    }

}