Question

所以我对android很新，我正在研究android网站上的一些示例代码。我现在正在看的那个叫做通知用户：http://developer.android.com/training/notify-user/index.html。

示例非常简单，用户以秒为单位输入时间和消息，并在后台设置计时器。一旦时间用完，就会通知用户。

所以这是activity_main.xml的副本

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <TextView
        android:id="@+id/seconds_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="32dp"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="@string/ping_text" />

    <EditText
        android:id="@+id/edit_seconds"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/seconds_view"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="15dp"
        android:ems="10"
        android:text="@string/seconds_default"
        android:inputType="numberSigned">

        <requestFocus />
    </EditText>

    <TextView
        android:id="@+id/reminder_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/edit_seconds"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="40dp"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="@string/reminder_label" />

    <EditText
        android:id="@+id/edit_reminder"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/edit_seconds"
        android:layout_below="@+id/reminder_view"
        android:layout_marginTop="15dp"
        android:ems="10"
        android:text="@string/reminder_text"
        android:inputType="textMultiLine" />

    <Button
        android:id="@+id/ping_button"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/edit_reminder"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="25dp"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:onClick="onPingClick"
        android:text="@string/ping" />

</RelativeLayout>

您可以看到有两个编辑视图供用户输入秒（edit_seconds）和消息（edit_reminder）。还有一个名为ping的按钮，当按下时将数据发送到ServiceIntent。

以下是mainactivity.java的代码：

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.example.android.pingme;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {

    private Intent mServiceIntent;

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

        // Creates an explicit Intent to start the service that constructs and
        // issues the notification.
        mServiceIntent = new Intent(getApplicationContext(), PingService.class);
    }

    /*
     * Gets the values the user entered and adds them to the intent that will be
     * used to launch the IntentService that runs the timer and issues the
     * notification.
     */
    public void onPingClick(View v) {
        int seconds;

        // Gets the reminder text the user entered.
        EditText msgText = (EditText) findViewById(R.id.edit_reminder);
        String message = msgText.getText().toString();

        mServiceIntent.putExtra(CommonConstants.EXTRA_MESSAGE, message);
        mServiceIntent.setAction(CommonConstants.ACTION_PING);
        Toast.makeText(this, R.string.timer_start, Toast.LENGTH_SHORT).show();

        // The number of seconds the timer should run.
        EditText editText = (EditText)findViewById(R.id.edit_seconds);
        String input = editText.getText().toString();

        if(input == null || input.trim().equals("")){
            // If user didn't enter a value, sets to default.
            seconds = R.string.seconds_default;
        } else {
            seconds = Integer.parseInt(input);
        }
        int milliseconds = (seconds * 1000);
        mServiceIntent.putExtra(CommonConstants.EXTRA_TIMER, milliseconds);
        // Launches IntentService "PingService" to set timer.
        startService(mServiceIntent);

从上面的onPingClick（View v）方法可以看出，editTexts都引用了变量“msgText”和“editText”。然而，ping按钮从未被引用，也没有附加到按钮的监听器，因此它在按下按钮时启动服务。但是，该应用程序可以在模拟器和手机上完美运行，而无需引用按钮。

android如何知道单击按钮意味着必须对onPingClick（View v）的方法进行操作？

Answer 1

因为在指定Button的xml布局中：android:onClick="onPingClick"
这会在Java代码之外设置onClickListener。

请注意，方法符合签名：

public void someName(View v)

这是为视图设置Click Listener的另一种方法。

Android站点中的通知示例

1 个答案: