android studying

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1、按键改变背景颜色
//MainActivity.java

package com.xiaod.hello;

import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;
import android.widget.Button;

public class MainActivity extends Activity {
@Override

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    final TextView tvHello = (TextView) findViewById(R.id.tvHello);

    Button btnRed = (Button) findViewById(R.id.btnRed);
    Button btnGreen = (Button) findViewById(R.id.btnGreen);

    btnRed.setOnClickListener(new OnClickListener() {
    public void onClick(View view) {
      tvHello.setText("click");
      tvHello.setBackgroundColor(Color.RED);
    }
    });

    btnGreen.setOnClickListener(new OnClickListener() {
    public void onClick(View view) {
      tvHello.setText("click");
      tvHello.setBackgroundColor(Color.GREEN);
    }
    });
}
}
//main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" android:orientation="vertical">
    <TextView android:text="TextView"
    android:id="@+id/textAlphaValue"
    android:layout_height="wrap_content"
    android:layout_width="match_parent">
    </TextView>
    <ImageView android:id="@+id/image"
    android:src="@drawable/laopo"
    android:layout_height="wrap_content"
    android:layout_width="match_parent">
    </ImageView>
</LinearLayout>

2、上下左右按键改变图片透明度
//main.java

package com.xiaod.keyevent;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.widget.ImageView;
import android.widget.TextView;

public class Main extends Activity {
    /** Called when the activity is first created. */
private TextView mAlphaValueText;
private int mAlaphaValue;
private ImageView mImage;
private static final String TAG = "KeyEvent";
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mAlphaValueText = (TextView) findViewById(R.id.textAlphaValue);
        mAlaphaValue = 900;
        mImage = (ImageView) findViewById(R.id.image);
        mImage.setAlpha(mAlaphaValue);
        mAlphaValueText.setText("Alpha = " + mAlaphaValue*100/0xff + "%");
    }
    public boolean onKeyDown(int keyCode, KeyEvent msg) {
    Log.v(TAG, "onKeyDown: keyCode = " + keyCode);
    Log.v(TAG, "onKeyDown: String = " + msg.toString());

    switch(keyCode) {
    case KeyEvent.KEYCODE_DPAD_UP:
    case KeyEvent.KEYCODE_DPAD_RIGHT:
      mAlaphaValue += 10;
      break;
    case KeyEvent.KEYCODE_DPAD_LEFT:
    case KeyEvent.KEYCODE_DPAD_DOWN:
      mAlaphaValue -= 10;
      break;
    default:
      break;
    }

    if(mAlaphaValue > 0xFF)
      mAlaphaValue = 0xFF;
    if(mAlaphaValue < 0x0)
      mAlaphaValue = 0x0;

    mImage.setAlpha(mAlaphaValue);
    mAlphaValueText.setText("Alpha = " + mAlaphaValue*100/0xff + "%");
    return super.onKeyDown(keyCode, msg);
    }
}

//main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" android:orientation="vertical">
    <TextView android:text="TextView"
    android:id="@+id/textAlphaValue"
    android:layout_height="wrap_content"
    android:layout_width="match_parent">
    </TextView>
    <ImageView android:id="@+id/image"
    android:src="@drawable/laopo"
    android:layout_height="wrap_content"
    android:layout_width="match_parent">
    </ImageView>
</LinearLayout>

补充：移动开发 , Android ,