《Android 基础（十六）》Toast

介绍

A toast provides simple feedback about an operation in a small popup. It only fills the amount of space required for the message and the current activity remains visible and interactive. For example, navigating away from an email before you send it triggers a “Draft saved” toast to let you know that you can continue editing later. Toasts automatically disappear after a timeout.

翻译：
Toast以一种小弹框的方式来给予用户反馈，它只需要消息可以显示出来的那小部分空间，同时Activity依然可见可交互。例如，当你写邮件的时候退出，会触发“草稿已保存”的Toast来让你知道你以后可以继续编辑这封邮件。Toast会在一段时间后自己消失。

类结构

Toast成员

这里写图片描述

成员介绍

成员	含义
Toast(Context)	构造函数
show()	显示Toast
cancel()	取消Toast
setMargin(float,float)	设置横向的margin和纵的margin
setGravity(int ,int, int)	设置toast的位置重心相对的XOffset, YOffset
makeText(Context, CharSequence, int)	利用字符串创建Toast
makeText(Context, int, int)	利用字符串资源创Toast
setView(View)	设置自定义Toast显示View
setDuration(int)	设置Toast的显示时间
setText	设置Message文本内容

基本使用

布局文件

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="mraz.com.toastdemo.MainActivity">

    <Button
        android:id="@+id/bt_simple"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorAccent"
        android:text="Simple Toast" />

    <Button
        android:id="@+id/bt_custom"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="30dp"
        android:background="@color/colorPrimary"
        android:text="Custom Toast" />
</LinearLayout>

自定义的Toast布局
custom_toast.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="40dp"
    android:background="@drawable/shape_bg"
    android:orientation="horizontal">

    <ImageView
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:src="@drawable/ic_account_circle_black_24dp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="40dp"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp"
        android:gravity="center"
        android:text="This is a Custom Toast !"
        android:textStyle="italic" />
</LinearLayout>

代码内容

package mraz.com.toastdemo;

import android.content.Context;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    Context mContext;
    Button btSimple, btCustom;

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

        mContext = this;

        btSimple = (Button) findViewById(R.id.bt_simple);
        btCustom = (Button) findViewById(R.id.bt_custom);

        btSimple.setOnClickListener(this);
        btCustom.setOnClickListener(this);

    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.bt_simple:
                Toast.makeText(mContext, " This is a simple toast", Toast.LENGTH_SHORT).show();
                break;
            case R.id.bt_custom:
                LayoutInflater layoutInflater = LayoutInflater.from(mContext);
                View custToast = layoutInflater.inflate(R.layout.custom_toast, null);
                Toast toast = new Toast(mContext);
                toast.setView(custToast);
                toast.setDuration(Toast.LENGTH_SHORT);
                toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
                toast.show();
                break;
        }
    }
}