最近寫了一個下載圖片的程式，但當時卻沒考慮到下載進度的顯示，要是圖檔很大的時侯，程式可能就會畫面停格，使用者也會一頭霧水。後來我把ProgressBar這個元件拿進來用，我想在按下按鈕後，可以進行圖檔下載，並顯示ProgressBar，當下載完畢後就隱藏ProgressBar，並把下載到的圖片給顯示在畫面上。
ProgressBar根據Style區分為四種，其中三種是轉圈圈的動態圖示，另一種是長型的進度條。
以下就是一個轉圈圈的ProgressBar
<ProgressBar
android:id="@+id/progressBar1"
style="?android:attr/progressBarStyleLarge"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
根據畫面大小顯示位置，您可以自行設定為中型還是小型的圖示
style="?android:attr/progressBarStyleLarge" 大型尺寸
style="?android:attr/progressBarStyleSmall" 小型尺寸若沒有填寫，則預設為中型尺寸。
activity_main.xml
<Button
android:id="@+id/buttonClick"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="按我下載圖片"/>
<ImageView
android:id="@+id/ivImage"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@+id/buttonClick"
android:layout_marginTop="20dp"
android:visibility="gone" />
<ProgressBar
android:id="@+id/progressBar1"
style="?android:attr/progressBarStyleLarge"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/buttonClick"
android:layout_alignRight="@+id/buttonClick"
android:layout_below="@+id/buttonClick"
android:layout_marginTop="20dp"
android:visibility="gone" />
MainActivity
private Button btnClick;
private ProgressBar progressbar1;
private ImageView imageView;
private String urlPath = "";
private String[] urls = {"https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-frc3/1477341_10151905232591588_655832224_n.png",
"https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-prn1/t1/29552_10151712215411588_739185948_n.png",
"https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-prn1/t1/73998_10151252154266588_140103885_n.png"};
private byte[] data = null;
private int loadindex = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnClick = (Button) findViewById(R.id.buttonClick);
progressbar1 = (ProgressBar) findViewById(R.id.progressBar1);
imageView = (ImageView) findViewById(R.id.ivImage);
btnClick.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
btnClick.setClickable(false);
if(loadindex==urls.length){
loadindex = 0;
}
urlPath = urls[loadindex];
loadindex++;
data = null;
progressbar1.setVisibility(View.VISIBLE);
imageView.setVisibility(View.GONE);
Thread thread = new Thread(new Runnable() {
public void run() {
try {
data = loadData();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
runOnUiThread(new Runnable() {
public void run() {
progressbar1.setVisibility(View.GONE);
Bitmap bm = BitmapFactory.decodeByteArray(data, 0, data.length);
imageView.setImageBitmap(bm);
imageView.setVisibility(View.VISIBLE);
btnClick.setClickable(true);
}
});
}
});
thread.start();
}
});
}
private byte[] loadData() throws Exception {
InputStream inputstream;
URL url = new URL(urlPath);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
inputstream = conn.getInputStream();
ByteArrayOutputStream outputstream = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = -1;
while ((len = inputstream.read(buffer)) != -1) {
outputstream.write(buffer, 0, len);
}
inputstream.close();
outputstream.close();
return outputstream.toByteArray();
}因為會下載Internet圖片，所以在AndroidManifest.xml 要加入這行設定。
這樣就可以達到下載圖片時顯示ProgressBar，但是繞圈圈可能不是我們想要的，看起來是有點弱掉了，我也想要 像"賴"在下載圖片時有橫條式的PROGRESSBAR和下載大小文字顯示。
首先先更改progressbar的style，我順便改了一下顯示寬度。
activityxml.xml <ProgressBar android:id="@+id/progressBar1" style="?android:attr/progressBarStyleHorizontal" android:layoutwidth="matchparent" android:layoutheight="wrap_content"/>
執行結果後，蛤~ 不會動。
原來橫條ProgressBar 是要先設定初始值，要動態顯示進度條就要設定值給它。。
activity_main.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=".MainActivity" >
<Button
android:id="@+id/buttonClick"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="按我下載圖片" />
<ImageView
android:id="@+id/ivImage"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@+id/buttonClick"
android:layout_marginTop="20dp"
android:visibility="gone" />
<ProgressBar
android:id="@+id/progressBar1"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/buttonClick"
android:layout_alignRight="@+id/buttonClick"
android:layout_below="@+id/buttonClick"
android:layout_marginTop="20dp"
android:visibility="gone" />
<TextView
android:id="@+id/progressText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/buttonClick"
android:layout_alignRight="@+id/buttonClick"
android:layout_below="@+id/progressBar1"
android:layout_marginTop="20dp"
android:gravity="center" />
MainActivity
protected static final int PROGRESS = 0x10000;
private Button btnClick;
private ProgressBar progressbar1;
private TextView progressText;
private ImageView imageView;
private String urlPath = "";
private String[] urls = {
"https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-frc3/1477341_10151905232591588_655832224_n.png",
"https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-prn1/t1/29552_10151712215411588_739185948_n.png",
"https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-prn1/t1/73998_10151252154266588_140103885_n.png" };
private byte[] data = null;
private int loadindex = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnClick = (Button) findViewById(R.id.buttonClick);
progressbar1 = (ProgressBar) findViewById(R.id.progressBar1);
progressText = (TextView) findViewById(R.id.progressText);
imageView = (ImageView) findViewById(R.id.ivImage);
btnClick.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
btnClick.setClickable(false);
if (loadindex == urls.length) {
loadindex = 0;
}
urlPath = urls[loadindex];
loadindex++;
data = null;
progressbar1.setVisibility(View.VISIBLE);
progressbar1.setMax(100); // 設定最大值是100
progressbar1.setProgress(0); // 設定目前進度0
progressText.setText("");
progressText.setVisibility(View.VISIBLE);
// progressbar2.setVisibility(View.VISIBLE);
// progressbar3.setVisibility(View.VISIBLE);
// progressbar4.setVisibility(View.VISIBLE);
imageView.setVisibility(View.GONE);
Thread thread = new Thread(new Runnable() {
public void run() {
try {
data = loadData();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
runOnUiThread(new Runnable() {
public void run() {
progressbar1.setVisibility(View.GONE);
progressText.setVisibility(View.GONE);
Bitmap bm = BitmapFactory.decodeByteArray(data,
0, data.length);
imageView.setImageBitmap(bm);
imageView.setVisibility(View.VISIBLE);
btnClick.setClickable(true);
}
});
}
});
thread.start();
}
});
}
private byte[] loadData() throws Exception {
InputStream inputstream;
URL url = new URL(urlPath);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
inputstream = conn.getInputStream();
ByteArrayOutputStream outputstream = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = -1;
int totalSize = conn.getContentLength();
int downloadSize = 0;
while ((len = inputstream.read(buffer)) != -1) {
outputstream.write(buffer, 0, len);
downloadSize = downloadSize + len;
Message msg = new Message();
msg.what = PROGRESS;
msg.arg1 = totalSize;
msg.arg2 = downloadSize;
mHandler.sendMessage(msg);
}
inputstream.close();
outputstream.close();
return outputstream.toByteArray();
}
//設定ProgressBar進度
private Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case PROGRESS:
int total = msg.arg1;
int current = msg.arg2;
Log.i("progress:", current + "/ " + total);
int count = current * 100 / total;
progressbar1.setProgress(count);
progressText.setText(current + "/" + total);
break;
}
}
};加上ProgressBar處理的部份，這時下載橫條ProgressBar也能顯示進度，再輔助下載大小文字顯示，這樣一來效果更親民了，打完收工。
Android 調用照相機功能，取得照片原圖、縮圖的方法
最近在研究可以開啟手機相機功能，拍完照取出照片的方法。爬了許多文章，發現光是開啟相機前置處理就會影響取出相片時的處理方法。
最基本的調用相機方法：
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(intent, 0);
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
這行就是利用intent去開啟Android的照相機介面，再然後拍完照，即呼叫onActivityResult
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_OK) {
Bitmap mbmp = (Bitmap) data.getExtras().get("data");
imgMicro.setImageBitmap(mbmp);
}
}
而(Bitmap) data.getExtras().get("data"); 就可以取到照片的"縮圖"，沒有錯！只是縮圖。官方文件有說明，android系統分配給每個應用程式的最大內存記憶體是16M，為了防止佔用內存記憶體過大(OutOfMemory)，所以把相機拍完回傳的照片經過壓縮。但是我想要再拍完照後可以直接取到原圖，有許多前輩對於這樣情況，對於叫用相機前startActivityForResult(intent, 0); 做了一些修改。
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
File tmpFile = new File(Environment.getExternalStorageDirectory(),"image.jpg");
Uri outputFileUri = Uri.fromFile(tmpFile);
intent.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri);
startActivityForResult(intent, 0);
File tmpFile = new File(Environment.getExternalStorageDirectory(),"image.jpg");
這行是 利用tmpFile先新增一張照片。在開啟Android的照相機介面時，把這張照片指定為輸出檔案位置。
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_OK) {
Bitmap bitmap = BitmapFactory.decodeFile(Environment
.getExternalStorageDirectory() + "/image.jpg");
imgLarge.setImageBitmap(bitmap);
}
}
拍完照將結果回傳時，可以透過 Environment.getExternalStorageDirectory() + "/image.jpg" 取得我們指定的圖片路徑。
這時侯Intent data則取不到縮圖資料了，若想要取得縮圖就要自己用bitmap原圖去產生縮圖。
Bitmap minibm = ThumbnailUtils.extractThumbnail(bitmap, minWidth, minHeight);
- minWidth 是縮圖的寬度
- minHeight 是縮圖的長度
最近在研究可以開啟手機相機功能，拍完照取出照片的方法。爬了許多文章，發現光是開啟相機前置處理就會影響取出相片時的處理方法。
最基本的調用相機方法：
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(intent, 0);
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
這行就是利用intent去開啟Android的照相機介面，再然後拍完照，即呼叫onActivityResult
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_OK) {
Bitmap mbmp = (Bitmap) data.getExtras().get("data");
imgMicro.setImageBitmap(mbmp);
}
}
而(Bitmap) data.getExtras().get("data"); 就可以取到照片的"縮圖"，沒有錯！只是縮圖。官方文件有說明，android系統分配給每個應用程式的最大內存記憶體是16M，為了防止佔用內存記憶體過大(OutOfMemory)，所以把相機拍完回傳的照片經過壓縮。但是我想要再拍完照後可以直接取到原圖，有許多前輩對於這樣情況，對於叫用相機前startActivityForResult(intent, 0); 做了一些修改。
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
File tmpFile = new File(Environment.getExternalStorageDirectory(),"image.jpg");
Uri outputFileUri = Uri.fromFile(tmpFile);
intent.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri);
startActivityForResult(intent, 0);
File tmpFile = new File(Environment.getExternalStorageDirectory(),"image.jpg");
這行是 利用tmpFile先新增一張照片。在開啟Android的照相機介面時，把這張照片指定為輸出檔案位置。
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == RESULT_OK) {
Bitmap bitmap = BitmapFactory.decodeFile(Environment
.getExternalStorageDirectory() + "/image.jpg");
imgLarge.setImageBitmap(bitmap);
}
}
拍完照將結果回傳時，可以透過 Environment.getExternalStorageDirectory() + "/image.jpg" 取得我們指定的圖片路徑。
這時侯Intent data則取不到縮圖資料了，若想要取得縮圖就要自己用bitmap原圖去產生縮圖。
Bitmap minibm = ThumbnailUtils.extractThumbnail(bitmap, minWidth, minHeight);
- minWidth 是縮圖的寬度
- minHeight 是縮圖的長度
