onClick 方法问题 [英] onClick method issue

问题描述

好的，所以我正在浏览 devoloper.android.com 网站上的MyFirstApp"教程.我在上一个教程，我已经为你可以说的第一章做了一切.唯一的事情是，在开始另一个活动"课程结束时，它会告诉您运行应用程序.好吧，当我运行它时，它会在模拟器上显示一个可单击的按钮，但是当您单击它时，它会出现运行时错误并强制关闭.我试图对此进行一些研究，但不知道发生了什么.错误是:java.lang.IlleglStateException: 在 android.widet.B 上的视图类的 onClick 处理程序的活动类 com.example.MyFirstApp.MainActivity 中找不到方法 sendmessage(view)我将展示代码:

ok, so I am going through the tutorial of the "MyFirstApp" on the devoloper.android.com site. I am on the last tutorial and I have did everything for the first chapter you can sorta say. The only thing is, at the end of "start another activity" lesson, at the end it tells you to run the app. Well when I run it, it appears with a clickable button on the emulator, but when you click it, it gets a runtime error and forces close. I have tried to do some research on this, but not a clue on what is going on. The error is: java.lang.IlleglStateException: Could not find a method sendmessage(view) in the activity class com.example.MyFirstApp.MainActivity for onClick handler on view class on android.widet.B I am going to show the code for this:

主活动:

package com.example.myfirstapp;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;

public class MainActivity extends Activity {
    public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";    

    /** Called when the user clicks the Send button */
    public void sendMessage(View view) {
        Intent intent = new Intent(this, DisplayMessageActivity.class);
        EditText editText = (EditText) findViewById(R.id.edit_message);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE,  message);
        startActivity(intent);
        // Do something in response to button
    }

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

activity_display_message:

activity_display_message:

<RelativeLayout 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: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=".DisplayMessageActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>

DisplayMessageActivity.java:

DisplayMessageActivity.java:

package com.example.myfirstapp;

import android.annotation.SuppressLint;
import android.annotation.TargetApi;
import android.app.ActionBar;
import android.app.Activity;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.view.MenuItem;
import android.widget.TextView;

public class DisplayMessageActivity extends Activity {

    @SuppressLint("NewApi")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Get the message from the intent
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

        // Create the text view
        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText(message);

        // Set the text view as the activity layout
        setContentView(textView);

        // Make sure we're running on Fry or higher to use ActionBar APIs
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.FROYO) {
            // Show the Up button in the action bar.
            getupActionBar().setDisplayHomeAsUpEnabled(true);
        }
    }

    private ActionBar getupActionBar() {
        // TODO Auto-generated method stub
        return null;
    }

    /**
     * Set up the {@link android.app.ActionBar}, if the API is available.
     */
    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    private void setupActionBar() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            getActionBar().setDisplayHomeAsUpEnabled(true);
        }
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case android.R.id.home:
            // This ID represents the Home or Up button. In the case of this
            // activity, the Up button is shown. Use NavUtils to allow users
            // to navigate up one level in the application structure. For
            // more details, see the Navigation pattern on Android Design:
            //
            // http://developer.android.com/design/patterns/navigation.html#up-vs-back
            //
            NavUtils.navigateUpFromSameTask(this);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

}

推荐答案

您在 xml 中似乎拼错了 Button onClick() 的函数名称.你的java代码中有一个大写的m"

It looks like you misspelled the function name in your xml for the Button onClick(). You have an uppercase "m" in your java code

 public void sendMessage(View view) {

你的 xml 中可能还有一个小写的m"

and probably a lowercase "m" in your xml

<Button
...
android:onClick="sendmessage"/>

为了符合java标准，在你的xml里改成

To comply with java standards, change it in your xml to

 android:onClick="sendMessage"/>

这篇关于onClick 方法问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！