因为安卓手机有屏幕自动旋转的功能，而横屏与竖屏对APP的视图变化有很大的影响，我们能够通过不同的方式来使这个影响降到最低
设置固定住屏幕方向：
landspace：使屏幕永远保持横屏，手机正常方向逆时针旋转90度；
portrait：使屏幕永远保持竖屏，即手机的正常方向；
当不设置固定屏幕方向时：
此时就得考虑在代码中解决横屏与竖屏所产生的问题
背景：每一次切换方向都是一次Activity的销毁与重建，这个过程不可，也不能避免，否则布局不会发生变化
解决办法：①创建两种状态时的不同布局
②保存数据使得状态的改变不会造成数据的丢失
代码：
#acticit_main.xml#
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical" >
<TextView
android:id="@+id/question_text_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="24dp"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="@+id/true_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/true_button"/>
<Button
android:id="@+id/false_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/false_button"/>
<Button
android:id="@+id/next_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/next_button" />
<Button
android:id="@+id/prev_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/prev_button" />
</LinearLayout>
</LinearLayout>MainActivity.java
package com.example.root.myapplication;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import static android.view.View.*;
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private static final String KEY_INDEX = "index";
private Button mTrueButton;
private Button mFalseButton;
private Button mNextButton;
private Button mPREVButton;
private TextView mQuestionTextView;
private Question[] mQuestionBank = new Question[] {
new Question(R.string.question_australia,true),
new Question(R.string.question_oceans, true),
new Question(R.string.question_mideast, true),
new Question(R.string.question_africa, true),
new Question(R.string.question_americas, true),
new Question(R.string.question_asia, true)
};
private int mCurrentIndex = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG, "onCreate(Bundle) called");
setContentView(R.layout.activit_main);
if(savedInstanceState != null){
mCurrentIndex = savedInstanceState.getInt(KEY_INDEX, 0);
}
mQuestionTextView = (TextView) findViewById(R.id.question_text_view);
mQuestionTextView.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
mCurrentIndex = (mCurrentIndex + 1) % mQuestionBank.length;
updateQuestion();
}
});
mTrueButton = (Button) findViewById(R.id.true_button);
mTrueButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v){
checkAnswer(true);
}
});
mFalseButton = (Button) findViewById(R.id.false_button);
mFalseButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v){
checkAnswer(false);
}
});
mNextButton = (Button) findViewById(R.id.next_button);
mNextButton.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
mCurrentIndex = (mCurrentIndex + 1) % mQuestionBank.length;
updateQuestion();
}
});
mPREVButton = (Button) findViewById(R.id.prev_button);
mPREVButton.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
mCurrentIndex = (mCurrentIndex - 1 + mQuestionBank.length) % mQuestionBank.length;
updateQuestion();
}
});
updateQuestion();
}
@Override
protected void onStart(){
super.onStart();
Log.d(TAG, "onStart() called");
}
@Override
protected void onResume(){
super.onResume();
Log.d(TAG, "onResume() called");
}
@Override
protected void onPause(){
super.onPause();
Log.d(TAG, "onPause() called");
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState){
super.onSaveInstanceState(savedInstanceState);
Log.i(TAG, "onSaveInstanceState");
savedInstanceState.putInt(KEY_INDEX, mCurrentIndex);
}
@Override
protected void onStop(){
super.onStop();
Log.d(TAG, "onStop() called");
}
@Override
protected void onDestroy(){
super.onDestroy();
Log.d(TAG, "onDestroy() called");
}
private void updateQuestion(){
int question = mQuestionBank[mCurrentIndex].getTextResId();
mQuestionTextView.setText(question);
}
private void checkAnswer(boolean userPressedTrue){
boolean answerIsTrue = mQuestionBank[mCurrentIndex].isAnswerTrue();
int messageResId = 0;
if(userPressedTrue == answerIsTrue){
messageResId = R.string.correct_toast;
}else{
messageResId = R.string.incorrect_toast;
}
Toast.makeText(this, messageResId, Toast.LENGTH_SHORT).show();
}
}
结果截图：
