android BMI实例改进

在使用UI组建，使用消息传递对象intent，及偏好设置

在MainActivity中代码：

public class MainActivity extends Activity {
/** Called when the activity is first created. */

private Button button_calc;
private EditText field_height;
private EditText field_weight;

protected static final int MENU_ABOUT = Menu.FIRST;
protected static final int MENU_QUIT = Menu.FIRST + 1;

private static final String TAG = "bmi";
private static final String PREF = "bmi_bref";
private static final String PREF_HEIGHT = "bmi_height";

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

findViews();
restorePrefs();
button_calc.setOnClickListener(calcBMI);
Log.d(TAG, "set listener");
}

@Override
protected void onStop() {
// TODO Auto-generated method stub
super.onStop();
SharedPreferences settings = getSharedPreferences(PREF, 0);
settings.edit().putString(PREF_HEIGHT, field_height.getText()
.toString()).commit();
}

private void restorePrefs() {
SharedPreferences settings = getSharedPreferences(PREF, 0);
String pref_height = settings.getString(PREF_HEIGHT, "");
if (pref_height != "") {
field_height.setText(pref_height);
field_weight.requestFocus();
}
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// TODO Auto-generated method stub
menu.add(0, MENU_ABOUT, 0, "关于");
menu.add(0, MENU_QUIT, 0, "退出");

return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onMenuItemSelected(int featureId, MenuItem item) {
switch (item.getItemId()) {
case MENU_ABOUT:
openOptionsDialog();
break;
case MENU_QUIT:
finish();
break;
}
return super.onMenuItemSelected(featureId, item);
}

private void findViews() {
button_calc = (Button) findViewById(R.id.bmiButton);
field_height = (EditText) findViewById(R.id.height);
field_weight = (EditText) findViewById(R.id.weight);
Log.d(TAG, "find Views");
}

private OnClickListener calcBMI = new OnClickListener(){

public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, ReportActivity.class);
Bundle bundle = new Bundle();
bundle.putString("KEY_HEIGHT", field_height.getText().toString());
bundle.putString("KEY_WEIGHT", field_weight.getText().toString());
intent.putExtras(bundle);
startActivity(intent);

}

};

//创建对话框
private void openOptionsDialog() {
//Toast.makeText(MainActivity.this, "确定", Toast.LENGTH_LONG).show();
new AlertDialog.Builder(MainActivity.this).setTitle(R.string.about_title)
.setMessage(R.string.about_msg).setPositiveButton(R.string.about_positive,
new DialogInterface.OnClickListener() {

public void onClick(DialogInterface dialog,
int which) {
}

}
).show();
}

}

在values文件夹中添加一个report.xml

创建内容<string name="report_title">BMI</string>
<string name="report_back">BMI结果</string>

在layout文件夹中页添加一个report.xml，代码是：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>

<Button
android:id="@+id/report_back"
android:layout_height="wrap_content"
android:layout_width="fill_parent"
android:text="@string/report_back"
/>

<TextView
android:id="@+id/result"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text=""
/>
<TextView
android:id="@+id/suggest"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text=""
/>

</LinearLayout>

在activity包中创建一个ReportActivity.java

代码是：

public class ReportActivity extends Activity {
private Button button_back;
private TextView view_result;
private TextView view_suggest;

@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.report);

findViews();
button_back.setOnClickListener(new OnClickListener() {

public void onClick(View v) {
DecimalFormat nf = new DecimalFormat("0.00");
Bundle bundle = getIntent().getExtras();
double height = Double.parseDouble(bundle.getString("KEY_HEIGHT")) / 100;
double weight = Double.parseDouble(bundle.getString("KEY_WEIGHT"));
double bmi = weight / (height * height);
view_result.setText("you bmi is: " + nf.format(bmi));

if (bmi > 25) {
view_suggest.setText(R.string.suggest_heavy);

} else if (bmi < 20) {
view_suggest.setText(R.string.suggest_light);
} else {
view_suggest.setText(R.string.suggest_average);
}

}

});
}

private void findViews() {
button_back = (Button) findViewById(R.id.report_back);
view_result = (TextView) findViewById(R.id.result);
view_suggest = (TextView) findViewById(R.id.suggest);
}

}
实现的效果是在运行后，在BMI界面中分别输入升高和体重，点击按钮将，界面将跳转到另一界面，再次点击界面可以看到结果；在点击返回或者home按钮后，可以看到之前的升高输入的值依然在（即SharedPreferences起的作用）

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