Question

我按照提示操作，当我提示时，EXTRA_MESSAGE为红色。我不知道哪里出错了。它来自这里： https://developer.android.com/training/basics/firstapp/starting-activity.html

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

   Intent intent = getIntent();

   String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

   TextView textView = new TextView(this);
   textView.setTextSize(40);
   textView.setText(message);

   ViewGroup layout = (ViewGroup) findViewById(R.id.activity_display_message);
   layout.addView(textView);
}

这是MainActivity.java

package com.example.a29185.google_android;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

import static android.provider.AlarmClock.EXTRA_MESSAGE;

public class MainActivity extends AppCompatActivity {

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

    }
}

它的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:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <EditText android:id="@+id/edit_message"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/edit_message" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_send"
        android:onClick="sendMessage"/>
</LinearLayout>

另一个名为DisplayMessageActivity.java的活动

package com.example.a29185.google_android;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.ViewGroup;
import android.widget.TextView;
import static android.R.id.message;
import static android.icu.lang.UCharacter.GraphemeClusterBreak.T;
import static android.provider.AlarmClock.EXTRA_MESSAGE;

public class DisplayMessageActivity extends AppCompatActivity {

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

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

        ViewGroup layout = (ViewGroup) findViewById(R.id.activity_display_message);
        layout.addView(textView);
    }
}

它的xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_display_message"
    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="com.example.a29185.google_android.DisplayMessageActivity">

</RelativeLayout>

Answer 1

在MainActivity删除此行：

import static android.provider.AlarmClock.EXTRA_MESSAGE;

并添加以下内容：

...
public class MainActivity extends AppCompatActivity {

    // Your message string
    public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE" 

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...

当我运行app google guide.EXTRA_MASSAGE总是红色？

1 个答案: