Android：無法更改Fragment中按鈕的背景（可繪制）

Question

我有以下無法解決的問題：

我正在構建具有多個片段的android應用。 在第二個片段上，有一個按鈕，每次按下該按鈕時，都需要更改背景（即可繪制對象）。 在我添加更多邏輯之前，我希望它能夠正常工作，但是我無法使其正常工作。 非常感謝幫助！

round_button_f2_decrease.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list
    xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape android:shape="oval">
            <solid android:color="@color/colorButtonF1Decrease" />
        </shape>
    </item>
    <item
        android:drawable="@drawable/ic_trending_down_white_24px"
        android:gravity="center" />
</layer-list>

round_button_f2_increase.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape android:shape="oval">
            <solid android:color="@color/colorButtonF1Increase" />
        </shape>
    </item>
    <item
        android:drawable="@drawable/ic_trending_up_white_24px"
        android:gravity="center" />
</layer-list>

fragment_two.xml

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/f2_tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="Placeholder"
        android:textAlignment="center"
        android:textSize="40sp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/f2_button"
        android:layout_width="56dp"
        android:layout_height="56dp"
        android:layout_marginBottom="24dp"
        android:layout_marginEnd="24dp"
        android:elevation="2dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

</android.support.constraint.ConstraintLayout>

FragmentTwo.java

import android.graphics.drawable.Drawable;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;

public class FragmentTwo extends Fragment {
    private static final String TAG = "FragmentTwo";

    private Button mbtnSort;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_two, container, false);

        mbtnSort = view.findViewById(R.id.f2_button);
        mbtnSort.setBackground(getResources().getDrawable(R.drawable.round_button_f2_decrease));
        mbtnSort.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Drawable btnBackground = mbtnSort.getBackground();
                if (btnBackground.equals(getResources().getDrawable(R.drawable.round_button_f2_decrease))) {
                    Toast.makeText(getActivity(), "IF", Toast.LENGTH_LONG).show();
                    mbtnSort.setBackground(getResources().getDrawable(R.drawable.round_button_f2_increase));
                } else {
                    Toast.makeText(getActivity(), "ELSE", Toast.LENGTH_LONG).show();
                    mbtnSort.setBackground(getResources().getDrawable(R.drawable.round_button_f2_decrease));
                }
            }
        });
        return view;
    }
}

Answer 1

采用

mbtnSort.setBackground(R.drawable.round_button_f2_decrease);

Answer 2

現在可以正常工作：

public class FragmentThree extends Fragment {
    private static final String TAG = "FragmentThree";

    private Button mbtnSort;
    private boolean mbtnPressed = false;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_three, container, false);

        mbtnSort = view.findViewById(R.id.f3_button);
        mbtnSort.setBackgroundResource(R.drawable.round_button_f2_decrease);
        mbtnSort.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mbtnPressed == true) {
                    Toast.makeText(getActivity(), "IF", Toast.LENGTH_LONG).show();
                    mbtnSort.setBackgroundResource(R.drawable.round_button_f2_decrease);
                    mbtnPressed = false;
                } else {
                    Toast.makeText(getActivity(), "ELSE", Toast.LENGTH_LONG).show();
                    mbtnSort.setBackgroundResource(R.drawable.round_button_f2_increase);
                    mbtnPressed = true;
                }
            }
        });
        return view;
    }
}

Answer 3

我想我了解您要如何在不改變背景的情況下解決您的問題？

我在搜尋您很多東西，以了解如何扎根，並使用round_button_f2_decrease.xml進行檢查

所以很難

如果您用旗幟或其他東西來做，這將對您現在的問題有所幫助

我發現這可能有助於比較android中的兩個drawable

和兩個可繪制對象之間的比較資源