Question

我最近一直关注Android Studio教程（或者是tutoriel，对于那些粉丝们而言）。

我已经达到'开始另一个活动'阶段（link）。在这里我遇到了一些麻烦。该教程告诉我在'content_display_message.xml'文件中插入'android：id = @ + id / content“＆gt;。

我已经这样做了，但是AS说它出乎意料吗？

然后我忽略了这个错误，我遇到了一个问题。当我添加

RelativeLayout layout = (RelativeLayout) findViewById(R.id.content);

进入DisplayMessageActivity.java文件，出现了一个错误，说明'内容'未定义。我很确定我做了我的任务，而且我不确定是什么导致了这样的错误。

我的完整代码在这里：

DisplayMessageActivity.java：

package com.example.denny.myfirstapp;

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.RelativeLayout;
import android.widget.TextView;

public class DisplayMessageActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_display_message);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null)
                        .show();
            }
        });
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        Intent intent = getIntent();
        String message = intent.getStringExtra(MyActivity.EXTRA_MESSAGE);
        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText(message);

        RelativeLayout layout = (RelativeLayout) findViewById(R.id.content);
        layout.addView(textView);
    }
}

content_display_message.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.denny.myfirstapp.DisplayMessageActivity"
    tools:showIn="@layout/activity_display_message">
    android:id="@+id/content">
</RelativeLayout>

Answer 1

xml无效，请将xml更改为

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.denny.myfirstapp.DisplayMessageActivity"
    tools:showIn="@layout/activity_display_message" // Changed this line
    android:id="@+id/content">
</RelativeLayout>

Android Studio教程错误

1 个答案: