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FindViewById

activity_xml

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<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context="com.gclue.uisample.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:id="@+id/testView1"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

android:idでTextViewに名前をつけます。

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android:id="@+id/testView1"

こうすることで、プログラムからは、

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View.findViewById()

でXMLで記述されたViewをプログラムに取り込むことが可能になります。

http://developer.android.com/intl/ja/reference/android/view/View.html

MainActivity.java

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package com.gclue.uisample;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

/**
 * Skeleton of an Android Things activity.
 * <p>
 * Android Things peripheral APIs are accessible through the class
 * PeripheralManagerService. For example, the snippet below will open a GPIO pin and
 * set it to HIGH:
 * <p>
 * <pre>{@code
 * PeripheralManagerService service = new PeripheralManagerService();
 * mLedGpio = service.openGpio("BCM6");
 * mLedGpio.setDirection(Gpio.DIRECTION_OUT_INITIALLY_LOW);
 * mLedGpio.setValue(true);
 * }</pre>
 * <p>
 * For more complex peripherals, look for an existing user-space driver, or implement one if none
 * is available.
 *
 * @see <a href="https://github.com/androidthings/contrib-drivers#readme">https://github.com/androidthings/contrib-drivers#readme</a>
 */
public class MainActivity extends Activity {

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

        TextView mTextView = (TextView) findViewById(R.id.testView1);
        mTextView.setText("TEST Writing");
    }
}

TextViewの背景に色をつける

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<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context="com.gclue.uisample.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:id="@+id/testView1"
        android:background="#ff0000"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

TextViewの文字に色をつける

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<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context="com.gclue.uisample.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:id="@+id/testView1"
        android:background="#ff0000"
        android:textColor="#00ff00"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

TEXTのサイズを変える

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<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context="com.gclue.uisample.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:id="@+id/testView1"
        android:background="#ff0000"
        android:textColor="#00ff00"
        android:textSize="100px"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

TextViewのサイズを変える

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<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context="com.gclue.uisample.MainActivity">

    <TextView
        android:layout_width="200px"
        android:layout_height="200px"
        android:text="Hello World!"
        android:id="@+id/testView1"
        android:background="#ff0000"
        android:textColor="#00ff00"
        android:textSize="100px"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>