java - Android 开发人员 MyFirstApp 发送不起作用

Question

当我制作 MyFirstApp 项目(顺便将其命名为 SampleNotes)时，我使用内置 ADB 通过 wifi 在我的 CyanogenMod 10.1 Nook HD+ 上运行它，我尝试单击发送按钮，但它没有根本不做任何事；好像我从未添加任何有关 Intent 或第二个 Activity 的内容。有人可以帮忙吗？

MainActivity.java:

package com.example.samplenotes;

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.SampleNotes.MESSAGE";

    @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;
    }

    /**  Called when the user clicks the Send button */
    public void sendMessage(View view) {
        //Do something in response to button
        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);
    }

}

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.samplenotes"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.samplenotes.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.example.samplenotes.DisplayMessageActivity"
            android:label="@string/title_activity_display_message"
            android:parentActivityName="com.example.SampleNotes.MainActivity" >
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.example.SampleNotes.MainActivity" />
        </activity>
    </application>

</manifest>

DisplayMessageActivity.java:

package com.example.samplenotes;

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

public class DisplayMessageActivity extends Activity {

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

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

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

        setContentView(R.layout.activity_display_message);

        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:
            NavUtils.navigateUpFromSameTask(this);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

}

activity_main.xml:

  <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: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=".MainActivity"
        android:orientation="horizontal" >

        <EditText android:id="@+id/edit_message"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            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>

activity_display_message.xml:

<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>

字符串.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">SampleNotes</string>
    <string name="action_settings">Settings</string>
    <string name="hello_world">Hello world!</string>
    <string name="edit_message">Enter a message</string>
    <string name="button_send">Send</string>
    <string name="title_activity_display_message">My Message</string>

</resources>

Answer 1

正如其他人所说，要开始 Activity ，您需要调用:

startActivity();

此外，在 DisplayMessageActivity 中，在操作任何控件之前，必须首先设置布局:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    //first, set main layout
    setContentView(R.layout.activity_display_message);

然后获取 TextView 并设置它:

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

    TextView textView = (TextView) findViewById(R.id.text);
    textView.setTextSize(40);
    textView.setText(message);

并在您的activity_display_message.xml中添加id，以便可以检索您的textView:

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