第十三篇-通过Button设置文本背景颜色

MainActivity.java

package com.example.aimee.buttontest;

import android.annotation.SuppressLint;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.view.KeyEvent;

public class MainActivity extends AppCompatActivity {
    TextView textview;//声明全局变量

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final Button button1=(Button) findViewById(R.id.myButton1);
        final Button button2=(Button) findViewById(R.id.myButton2);
        final Button button3=(Button) findViewById(R.id.myButton3);

        textview=(TextView) findViewById(R.id.myTestView);
        final Drawable red_Drawable= ContextCompat.getDrawable(getBaseContext(),R.drawable.RED);
        final Drawable blue_Drawable= ContextCompat.getDrawable(getBaseContext(),R.drawable.BLUE);
        final Drawable yellow_Drawable= ContextCompat.getDrawable(getBaseContext(),R.drawable.YELLOW);

        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String str="You have clicked "+button1.getText().toString();
                textview.setText(str);
                if(textview.getBackground()!=red_Drawable){
                    textview.setBackground(red_Drawable);
                }
            }
        });

        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String str="You have clicked "+button2.getText().toString();
                textview.setText(str);
                if(textview.getBackground()!=blue_Drawable){
                    textview.setBackground(blue_Drawable);
                }
            }
        });

        button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String str="You have clicked "+button3.getText().toString();
                textview.setText(str);
                if(textview.getBackground()!=yellow_Drawable){
                    textview.setBackground(yellow_Drawable);
                }
            }
        });

        }

    @SuppressLint("ResourceAsColor")
    public boolean onKeyUp(int keyCode, KeyEvent event){
        CharSequence Charseq="Change your color here!";
        textview.setText(Charseq);
        final Drawable white_Drawable= ContextCompat.getDrawable(getBaseContext(),R.drawable.WHITE);
        textview.setBackground(white_Drawable);
//        textview.setBackgroundColor(0xFFFFFFFF);
        return super.onKeyUp(keyCode,event);
    }

    public boolean onKeyDown(int keyCode,KeyEvent event){
        CharSequence Charseq="You have pressed ";
        Charseq=Charseq+"a key!";
        textview.setText(Charseq);
        return super.onKeyDown(keyCode,event);
    }

}

 layout/colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="colorPrimary">#3F51B5</color>
    <color name="colorPrimaryDark">#303F9F</color>
    <color name="colorAccent">#FF4081</color>
    <drawable name="BLUE">#FF0000FF</drawable>
    <drawable name="BLACK">#FF000000</drawable>
    <drawable name="RED">#FFFF0000</drawable>
    <drawable name="YELLOW">#FFFFFF00</drawable>
    <drawable name="WHITE">#FFFFFFFF</drawable>
</resources>

activity_main.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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/myTestView"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/WHITE"
        android:text="@string/hello"
        android:textSize="36sp"
        app:layout_constraintLeft_toLeftOf="parent"

        app:layout_constraintRight_toRightOf="parent" />

    <Button
        android:id="@+id/myButton1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/myButtonText1"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent" />

    <Button
        android:id="@+id/myButton2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:text="@string/myButtonText2"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/myButton3"
        app:layout_constraintStart_toEndOf="@+id/myButton1" />

    <Button
        android:id="@+id/myButton3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:text="@string/myButtonText3"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

</android.support.constraint.ConstraintLayout>

这是一个简单的通过Button控制文本背景颜色的APP，值得注意的是其中的onKeyDown触发针对back，上下箭头键，或者还有其他一些键，没事，但是按字母键会很快被onKeyUp覆盖。

至于.java文件中注释了一句setBackGroundColor(int)，可以自行试试与setBackGround(drawable对象)有何不同。